If you do these 3 things, you have self-discipline, according to a psychology PhD

Getting up at 4 a.m. is not required. How can you tell if you have self-discipline? We all know people who work out at 5 a.m., eat only healthy food, and floss after every meal. And other people who sleep until the afternoon, chomp on untoasted Pop-Tarts, and then head out to have fun with their friends.