It's even harder to redefine yourself when you used to be good at whatever it was you lost, because you know just how much time and effort it took to get there. It can seem impossible to achieve the same level of mastery of anything else.
It's been almost 5 years since I quit and, while I've picked up new hobbies that I enjoy, I still haven't found anything that inspires the passion I used to have for my sport.