Coffee might be your saving grace to get through the workday, but caffeine on its own won't cut it in the long-run.

To stay passionate and excited about work, you're going to need to harness your inner motivation. It's stronger than a shot of espresso, and it can keep you going on even the most sleep-deprived and toughest of days.

Thankfully, science offers some solutions for tapping into your inner reserve of self-motivation daily.

Make a difference.

If you started your business or career hoping to make a difference in the world, give yourself a high five, and then habitually reflect on that vision to keep your self-motivation going.

In one study, the University of Michigan (Go Blue!) found that when call-center workers were trying to raise fundraising, they increased donations by 171 percent after speaking to students who benefited from the fundraising for a just a few minutes.

If you aren't aware of the difference your work is making, consider doing something similar. Talk to customers who benefit from your product, or seek out feedback from your manager. If you current efforts aren't making a dent in the world, it's never too late to switch careers or start a business.

Treat yourself.

Unsurprisingly, science says that 75 percent of what we do is motivated by rewards. What is surprising is how little most people actually reward themselves on a daily or weekly basis. Although we're all motivated by that big-ticket goal, like having a successful business or getting a promotion, those are far and between.

To keep your flame flickering during the weekly grind, consider treating yourself to a promotion. As long as you spend within reason, consider habitually tying a reward--like a bottle of wine or nice dinner--to a tough weekly project.

There is no win too small.

"I've found that small wins, small projects, small differences often make huge differences." --Rosabeth Moss Kanter, professor of business, Harvard University

Break your goal down into smaller milestones that you can reach and check off along the way. In her book The Entrepreneurial Instinct, author and investor Monica Mehta argues for the importance of understanding how the brain works in order to be successful in business.

Your brain holds onto information longer the more times that you succeed in something, allowing you to train yourself to complete set goals. Dopamine (a chemical in our brain) is released with each win, which makes us feel good--it is what gives us pleasure and inspiration, so when we start out on the next milestone, we are motivated to experience that feeling again, and are therefore more likely to reach that next small win.

Recharge the batteries.

"If we cannot disconnect, we cannot lead. Creating the culture of burnout is opposite to creating a culture of sustainable creativity." --Arianna Huffington

Do you feel like you're getting burned out? If so, you probably need that break more than ever right now. It might not seem like it, but relaxing with a pina colada (even if it's just for an extended weekend) is proved to boost motivation.

Can't travel to a tropical beach right now? Travis Bradberry suggests doing around 50 minutes of work followed by around 15 minutes of rest. Even if you don't want to follow his schedule, being aware of and prioritizing around your times of maximum productivity (and avoiding the infamous afternoon slump) will help you stay motivated.

Trick yourself.

You actually have the ability to trick (or train) your brain to view new habits differently-- that is, to see them as adding something positive into your life, rather than taking something away.

For instance, say you want to get motivated to wake up early: Start waking up two hours earlier than you have in the past, and think about it as adding two hours to your life every day, rather than focusing on missing out on two hours of sleep, and by the end of the week, you'll actually be adding an entire work day.

Get healthy.

A 2015 survey by Virgin Pulse found that the number one factor affecting employee motivation is health. Those results aren't surprising: it's hard--actually downright impossible--to expect employees to be motivated if they're in poor physical or emotional shape.

Getting enough rest and being in great shape are also essential for you to stay self-motivated. Even if you already eat your vegetables, working out daily can flood your brain with feel-good neurochemicals that will help you stay self-motivated daily.

Define your legacy.

Steve Jobs said he looked at himself in the mirror every single day and asked, "If today were the last day of my life, would I want to do what I am about to do today?"

It might seem a little morbid, but knowing that your time on earth is limited can be incredibly motivating. In one study by the University of Stamford, people who pictured an older version of themselves were able to get motivated and save much more for retirement.

Granted, you don't (and probably) shouldn't live everyday like it's your last. But to stay motivated, make a habit of moving toward your ideal future self. What steps are you taking to make a difference? How can you improve your life for the better this very week?

Do you have any tips for harnessing self-motivation? I'd love to hear them -- give me a shout-out on Twitter!