Would you rather be intelligent or disciplined? While most people would probably choose intelligence, discipline -- the ability to forgo immediate gratification in pursuit of a great goal -- is actually a greater predictor of subsequent life success.

“One great thing about self-control is that unlike other characteristics like intelligence, it’s easy to improve,” says Nathan DeWall, a psychology professor at the University of Kentucky who studies self-regulation (he’s also an ultra marathon runner).

Unfortunately, our amount of self-control finite; our reserve depletes over the course of the day, replenishing over night. This explains why people are more likely to lie, cheat or lash out as the day progresses and why, DeWall says, most violent crimes are committed after 10 p.m.

Related: How to Make Good Habits Stick

“Self-control is a powerful resource that is incredibly fragile,” he continues. “If I try and control my impulses now, it’s going to make a subsequent attempt at controlling my impulses later in the day a little bit harder.” Say you’re trying to eat healthy and you go out to lunch with friends -- you have to expend energy on both resisting the breadbasket as well as forgoing the burger in favor of a salad. “What's going to happen when I'm leaving the parking lot and someone cuts me off? DeWall asks. “I'm going to have less energy to help me override an angry impulse.”

Like a muscle, willpower can be strengthened. With practice and resistance training, our ability to control our impulses in pursuit of later, greater goals can grow, giving us the energy to easily resist that cookie and promptly file those taxes. Here’s how to increase your reserve.

1. Monitor your behavior.
It’s hard to practice self-control if you aren’t cognizant of your current behavior and routines. Want to lose weight? First you need to be aware of what you eat on a daily basis. Want a healthier bank account? You need to understand your current spending habits. DeWall’s friends who have kids often recount mindlessly eating their children’s leftovers – a Chicken McNugget here, a few French fries there. “Do that for two or three meals a week and you’re adding several hundred calories to your diet which will translate into multiple pounds every year,” says DeWall. Write down what you eat. Monitor your finances. Keep track.

Related: The Power of Mornings: Why Successful Entrepreneurs Get up Early

2. Form healthy habits.
At first, going to the gym will require self-control. You may to fight the urge to sit on the couch and watch TV. But over time, as going to the gym becomes a habit, it’s going to require much less willpower. It will start to feel automatic.

DeWall, who frequently runs ultra marathons over 100 miles long, recounts multiple conversations he’s had with fellow competitors. “They don’t believe that what they’re doing requires self-control,” he says. To them, it feels natural. As once hard activities begin to feel routine, they require less willpower; you have to fight yourself less and that frees up valuable energy that can be spent elsewhere.

3. Practice every day.
Just like practicing self-control in one aspect of your day (resisting a brownie, say) depletes the entire well, it also strengthens the entire muscle. “If I'm practicing self control in any domain, it should help me in all the others,” says DeWall. Multiple studies have illustrated that when you exercise self-control in one area of your life -- such as brushing your teeth with your non-dominant hand -- you can exert more willpower in another area, such as suppressing aggressive behavior. The two behaviors may be very different, but they share a common energy source.

Related: 10 Simple Ways to Eat Healthy Without Thinking

4. Control your environment.
Grocery stores are designed to play off our depleted willpower. “They don’t put produce by the checkout for a reason,” DeWall says. “They know you’ve just made a bunch of decisions; they know you're exhausted, so that’s where they put the junk food.”

You can’t, of course, change your supermarket’s layout, but you can control the environment at your home and at your work. It requires far less energy to resist a cookie if you know it’s not sitting in your cabinet. No solitaire on your desktop? Resisting starting up another game is instantly less of a struggle.

5. Make contracts to avoid arguing with yourself.
Decision-making can be exhausting. Fighting with yourself to go to the gym lots of work. DeWall suggests making contracts with yourself, thus taking the conflict out of difficult activities. “If I do this, then I’ll do that,” he says. “If I get home from work, then I’ll exercise for 10 minutes. It essentially takes you and your arguments with yourself out of the equation.”

6. Achieve balance.
Because on any given day we have a finite amount of willpower, it’s important that we don’t deplete the well too soon. Instead of simply writing down obligations on your calendar, rank them in terms of the energy or self-control they will require. “Become mindful of how much extra energy you are going to have to exert,” DeWall says. Catching up with a well-liked friend won’t require much exertion. But visiting your less-than-welcoming in-laws for the weekend? That may really sap you. If you know that in advance, you can adjust your week accordingly.

Related: How to Train Your Brain to Stay Focused