We’ve all used conversational expressions like "there aren't enough hours in the day" to describe a common sentiment--that if we had more time, we would all be more productive. However, this isn't always the case, and as you might suspect, the usual culprit for this feeling isn't a lack of time, but rather a mentality that either stifles productivity or leads to a misconception.

Take, for example, these seven scientific reasons why people feel like there isn't enough time:

1. You Don't Wake Up Early. The world runs on a 9-to-5 schedule. As a result, morning people tend to get more done and wind up more productive by the end of the work day. That isn't to say night people are inherently inferior--in fact, studies show that "night people" can be just as productive as morning people (or even more so)--but because the typical office, and our Western culture in general, start at nine sharp, they simply aren't able to match morning people in terms of workday productivity. Even if you consider yourself a night person, try waking up a little earlier each day, working iteratively if necessary, until you start having one or two extra hours each morning to accomplish new tasks.

2. You Multitask. Only a very, very small percentage of the population is good at multitasking. The rest of us are truly, definitively awful at it. When you try to accomplish two tasks at once, you instantly diminish your productivity at each individual task, thereby increasing the total amount of time it takes you to complete those tasks. What's worse is that many people believe themselves to be skilled multitaskers, and keep multitasking because they believe it will save them time. Repeat this process a few times a day, and a multitasker will feel as though he has saved a few hours of time--yet the tasks took hours more than they needed to. As a result, he feels like there simply isn't enough time in the day.

3. You Don't Practice Time Management. A review of time management literature recently concluded that the practice of time management strategies leads to more developed time management skills. That is to say, the more time you spend trying to manage your day, the better you'll become at it. This might seem obvious when put this way, but if you aren't regularly practicing time management, you might neglect the fact that your skills are going undeveloped. For example, you can't expect to be good at playing the guitar if you've only practiced once or twice in the past year. Get in the habit of actively managing your time.

4. You Aren't Getting Enough Rest. Scientific studies have consistently shown that insufficient or unhealthy sleep patterns can have a major impact on your long-term health and productivity. To put it succinctly, if you aren't sleeping adequately, you'll always perform worse than you ordinarily would, even with the aid of caffeine or other products. If you're performing slower than you otherwise would be, it's natural to feel like time is the problem--that there simply isn't enough time, rather than the fact that you aren't using your time well.

5. You're Too Concerned With Time. In Western cultures, we tend to be obsessed with time. We have to get to meetings on time. We're strict about our deadlines. We clock in at nine every morning and leave by five every day. This fixation on time can be a distraction--if you're checking the clock every few minutes to see how far you've come on a specific project (compared to where you "should" be), you'll almost always fall short of expectations. Projects take as long as they take, regardless of what your bosses or coworkers demand of you. Worrying yourself with the time is only going to slow you down.

6. You're Pessimistic. Even though we all measure time using the same devices, time itself can be a subjective experience. And as science has proven time and again, the positivity or negativity of your thoughts can have a significant impact on all your subjective experiences. In this context, if you are constantly pessimistic about the amount of time available to you, thinking thoughts like "there's no way I can get this done in time," or "I have too much to do today," you'll contribute to a feedback loop that makes you feel these things more often. In a sense, you contribute to your own feelings about time. Instead, try to focus on more positive elements of your day and appreciate the time you do have.

7. You're Too Engrossed in Your Work. This one comes with a caveat; as opposed to most of the items in this list, it's actually a good thing. In psychology, there's a phenomenon called flow, where a task you're particularly interested in fits a perfect balance of being approachable and challenging. While in flow, sometimes colloquially referred to as being "in your element" or "in the zone," you tend to be more productive and more focused, but you also tend to lose track of time. Do you ever look up at the clock and realized several hours have passed without your awareness or acknowledgment? That's a result of flow, and while it certainly isn't a bad thing, it can lead you to feel like you don't have enough time.

The next time you feel like there aren't enough hours in the day to do what needs done, remind yourself that time isn't something you can control. Instead, focus on the habits, thoughts, and beliefs that you can control, and work to make yourself more productive, more optimistic, and more focused on doing things well than doing things quickly.