I can't speak for the guy but I believe Luck has been suffering from depression for a few years now and an identity crisis, and this is how he's trying to end it. You spend your whole life playing football, it's a part of your identity, then suddenly your body just doesn't allow you to do it. There are expectations from everyone else and your own needs get put at the bottom of the list. Good for him for walking away on his own terms. Maybe some day he'll heal and try to come back, lord knows he's young enough. But right now this is what he needs.