Atomic Habits 13

 You will only succeed in making good habits and eliminating bad habits if you give yourself some immediate reward for when you do it. Your brain is wired to prioritize immediate rewards. It doesn't understand that if you go to the gym and sweat every day you'll be fit next year, so you need to give it a reward for going to the gym, but you need to be careful. Giving it a reward that is contrary to what you want, for example getting ice cream after you go out to the gym, is not going to help. It needs to be a reward that doesn't hurt the habit you're trying to make.