Belief is the fiction that’s a stimulus for positive action. The world dies a little bit when you stop believing in yourself.
The only reason to quit is to pivot somewhere else. Maybe it didn’t turn out exactly you had dreamed. Maybe it was too easy, or you lucked out.
People generally have two choices when choosing persistence: harness what you know and exploit it or explore more and see the world a bit differently. Time is just waiting for you to decide.