Practice pushing through pain
Running a hard mile gets very painful in a short amount of time. People who are used to running long-distance races never learn that particular kind of discomfort, and it’s hard for them to embrace the pain. Track intervals with short recoveries do that. You never fully recover before you start the next interval, and you’re never comfortable. You have to hurt during the race to get the time you want. It’s a different kind of runner’s high. You finish, you hurt, but you’re like, “Wooo!”