A great quote from an unknown author, which illustrates how the adversity can be a major catalyst to growth. The difficult times, situations, and events really can trigger an advancement in oneself that couldn't have been generated without them.
Joe Rogan has a great quote about constantly improving and how losses are not really losses at all:
You're always involved in improving yourself, you're a work in progress. And until you find those great fighters who are better than you don't realize what you need to work on.
More quotes on adversity here.