Stress
Being an NCAA football athlete is a full-time job. It's no easy feat attending daily practice and classes, completing homework, passing tests, going to and performing in games, feeding yourself, all while not having anxiety attacks. If you play college football, especially on a Division FBS team, you'll have to perform a perpetual juggling act.
The competitive season runs from August to January, but it's really a year-round sport. Given that most college football players spend more than forty hours a week practicing and conditioning (source), it can be a struggle to keep it all balanced.
Your coaches will want you in peak physical condition, your professors will want your undivided attention, and your mom will start nagging if she doesn't get her weekly phone call. Keep calm and tackle on. Or something like that.