Last year, I set a goal to exercise for at least 5 days each week for one month. Part of my deal to myself was that I would get a new book AFTER I achieved my goal. Rewarding myself motivated me to stay on track, but I had to find a reward that supported my efforts, not work against them.

Researchers have actually coined a term for rewarding your good behavior with something you think of as “bad”: self-licensing. An example would be going for a walk and then allowing yourself to have food you might otherwise avoid, like soda. A 185-pound person walking for 30 minutes at a leisurely pace would burn about 126 calories. Drinking a 12-oz, non-diet soda would add 140-195 calories. Depending on the soda, this person would add back all of the calories she burned off during the walk, and then some.

Anyone who has ever tried to track their calories might tell you that getting exact figures can be tricky. Different websites, activity trackers, exercise equipment, and other sources list different numbers of calories burned for the same activity! Even when writing this article, my coworker and I found different numbers for how many calories a short walk burns. Why is that? Exercise is complex! The number of calories burned depend on sex, age, body composition and size, exercise activity, and more. Even trackers, like AppleWatch or Fitbit, which has personalized information about you, don’t get their numbers exactly right.

Estimating calories burned in exercise is tricky and it is a big part of the reason we tend to over-reward with food! But now that you know how difficult it can be to accurately track calories, you can plan supportive rewards. It may also help to change the way you think about exercise! Research shows that we are more likely to reward ourselves when we “exercise” rather than engage in fun physical activity. Find ways to make exercise feel like fun (playing a game with a friend, walking to de-stress), and your physical activity will feel like its own reward—not something that requires one.

You can also think of exercise as something you do for your health, not a reason to eat more. That is, tell yourself to take a walk because you want to improve your health, not because you want to replace those calories with a treat. If you pay attention to your body, it will tell you when you need to eat more food because of your activity!

Most importantly, don’t beat yourself up if you do end up rewarding yourself a little too much! Becoming aware of this effect is one more tool to help you live your life in a healthy way, not another thing on the to-do list. Hopefully, it will be a tool that helps you live a little happier and healthier in 2019!