Purpose and reason.
Pain and adversity can make one great; look at Nietzsche, or Hemingway, or most famous artists, composers, and writers considered great. The thing is, greatness is like happiness; it can't be sought, it can't be striven for, it's a bi-product. Where happiness is a bi-product of meaning, greatness is a bi-product of pain. Unfortunately, greatness is not worth the price.