Like it or not, you have a limited amount of mental energy you can use to accomplish all your tasks in a given day. If you run out -- or don't start with much -- it's going to be a challenge to stay productive.

You're already doing things to manage your time, but are you doing anything to manage your mental energy? If not, you're not performing at your best.

The bad habits below will surely sap your mental energy and leave you without the resources to be productive. Start eliminating them and you'll see an improvement.

1. Not Having a Plan

This is a big one, and it's closely related to decision fatigue. The more decisions you have to make, the more mental energy you use. These could be big decisions, like what your college major should be, or little ones, like which shirt to wear.

No matter the weight of the decision, it takes energy. You might have heard of celebrities who have limited their decisions. Barack Obama, Steve Jobs, and Mark Zuckerberg all have a very limited wardrobe. Seth Godin eats the same thing for breakfast every day. These types of habits significantly reduce the number of decisions you need to make.

You don't have to go that far, but you should definitely have a plan.

Quick solutions: Each evening, make a plan for the following morning. Take on important tasks first. Keep an updated -- but manageable -- to-do list. Try time blocking. Anything you can do to eliminate the decision of what to do next will be a big help.

2. Over-Scheduling

Conversely, over-scheduling yourself can be detrimental as well. Many people find it easy to fill their schedules with various events. Work, family events, social outings, fitness goals, and everything else you want to do can lead to a very full calendar.

Decompression time is essential to lead a balanced life and maintain your mental energy. It's easy to forget about it, but its importance can't be overstated.

Quick solutions: Leave open slots in your day. You can use that time to decompress. You could organize your task list to better prioritize. Work on a side project that you love. Even just read a book.

3. Not Dealing With Clutter

You might think that tidying up isn't as important as being productive. But did you know that tidying up can make you more productive? Studies have shown that larger amounts of visual stimuli have a marked effect on the brain when you're trying to concentrate.

Clutter saps mental energy

It takes more mental energy to focus when you have things competing for your attention. Even if they're not ringing, vibrating, or otherwise actively interrupting you. Just having a lot of stuff around can make it harder to concentrate.

Quick solutions: Do your best to keep your work area -- and as many other areas as possible -- free from clutter. It'll help you stay focused, and it's just nice to be in a clean, organized environment. Can't find the joy in it? Try the famed KonMari Method or the KonMari app to begin with.

4. Procrastinating

When you're feeling mentally tired, it can be tempting to put things off. In some ways, it makes a lot of sense: if you're not able to perform your best, you may not want to work on an important project. But procrastination can take a big toll on your brain too.

It takes mental energy to even decide to do it now or put it off a little longer. Just the act to remember that you have to do it takes effort. All of that back-and-forth can really drain your reserves.

Quick solutions: Follow the two-minute rule: if you can accomplish something in two minutes, don't write it down. Just do it immediately. You can take a two-minute break from almost anything without getting super distracted.

5. Not Writing Things Down

The more pieces of information your juggle in your head, the more mental energy you're using. This is true if it's a grocery list, a thought about a weekend project, or someone's phone number. Not writing these things down means your brain has to store them, and then recall them when they're needed.

Going back to look something is also very easy, because you know where it is. Keeping things in your working memory is hard, but writing them down is super easy. And with great note-taking apps, you can always find what you wrote down, even if it gets buried under tons of other stuff.

Quick solution: Write stuff down. When you write it down, you're telling your brain not to worry about it (though some people find that writing something down further embeds it into their memory, which is also very valuable).

6. Perfectionism

"Satisficing" is a word that I've come to love. Satisficing is, essentially, finding an option that's satisfactory and going with it. If you're writing a blog post, you could spend hours and hours making it perfect. Or you could determine at what point it's satisfactory and stop there.

This doesn't mean you do shoddy work. It just means that you understand when your efforts are no longer being rewarded by results at a rate that's acceptable to you. In many cases, no one is going to notice, either. Are you slaving over an email to your boss? Is she going to spend more than two seconds reading it?

Quick solution: Ask yourself questions you need to ask when satisficing. Instead of using a ton of mental energy to make something perfect, just spend enough time to make it good enough. It doesn't sound nearly as good, but in almost every case, it is.

7. Multitasking

You should probably know this by now. Studies have shown that multitasking is very cognitively inefficient. There's a "switching cost" when you go from one task to another. Put simply, that cost places a drain on your mental energy.

I'll be the first to admit that some people are good at multitasking. If you find that it works for you, great. Go for it. But most people are way more efficient when they're focusing on a single thing.

Quick solution: Make single-tasking a habit. Use a Pomodoro timer to really get yourself to focus on a single task for 25 minutes, then let your brain take a quick break. Or use the 52/17 method. Or any other type of system that gets you to focus on one thing at a time. Try the excellent Marinara Timer or even the simple timer on your smartphone to start those work sprints.

8. Eating Poorly

What you eat has a huge effect on your mental energy. High glycemic index foods, like white bread, white rice, and anything with refined sugar will give you an energy spike. But that's followed by a big dip. And when that dip hits, you get tired -- which means you probably won't be getting much done.

But lower glycemic index foods, like whole grains, fruits and vegetables, and good sources of protein, will give you an even boost to your energy. It doesn't hit as fast, but it lasts a lot longer. That more predictable and gradual boost will be a big help.

Quick solutions: Making small improvements to your diet can make a big difference. Eat nuts and seeds, fish, fresh berries, and other "brain foods" to give your mental energy a boost. And don't get super hooked on caffeine. It helps, but only in the short term. Although when you do need a short-term solution, you'll want one of these best energy drinks for a quick boost.

9. Not Drinking Enough Water

Make sure you're drinking enough water. Exactly what "enough water" means is up for debate, but aiming for six to eight glasses of water a day should keep you hydrated. Even a very small drop in your hydration levels can have a big effect on you.

Drinking water helps boost mental energy

Drinking water instead of soda, coffee, or tea isn't always easy. But a big glass of water when you're feeling the drain of the day can make a huge difference in your energy level. Don't underestimate it.

Quick solution: If, like me, you have a hard time drinking water, try an app like My Water Balance. It will show you how much you've had to drink, tell you how much you have left to go, and help you stay motivated. Android users can try the popular Water Drink Reminder app.

10. Not Getting Enough Sleep

While other things can recharge your mental energy, nothing does it like sleep. Getting high-quality sleep -- and enough of it -- ensures that you have enough energy to do the things you need to do. But it's easy to miss out on the benefits of sleep.

If you're not sleeping enough, you're going to be mentally sluggish. You can negate some of those effects with caffeine, but you'll develop a tolerance. And you can get used to a little less sleep, but you'll probably find that you have a lower limit.

Quick solution: Make sure to sleep as much as your body is telling you to. If you're tired all day, you need more sleep. Most people need around eight hours, so start with that. And do what you can to make sure the sleep you're getting is effective.

11. Putting Off the Things You Love

Even if you plan well, make time to decompress, focus on a single thing at a time, and take the rest of the pieces of advice in this article, it can be easy to put off the things you love. Whether it's learning a new skill, working on a project, playing games, or reading, these things are extremely important.

study by San Francisco State University organizational psychologist Kevin Eschleman also showed how a creative outlet outside the office boosted workplace productivity and prevented burnout.

Quick solution: If you have to put it on your calendar, do so. Maybe it's easier to start your day with 20 minutes of your favorite hobby (I love to read novels while I eat breakfast). Or set aside an entire weekend day. Whatever you like to do that relieves stress, gets you to smile, and helps you enjoy your time is worth scheduling on your calendar.

How Do You Manage Your Mental Energy?

There are millions of things, both large and small, that drain your mental energy, from mundane tasks that you do every day to life-changing decisions. But if you take care to develop good habits, you'll find that you can significantly increase your mental energy reserves. The advice above is a great place to start.

But we're sure there are other great strategies out there, too. And we want to hear your best tips.

How do you stave off mental exhaustion? Share your best mental-energy-boosting tips in the comments below!

Image Credits: ESB Professional/Shutterstock