Most of these are equally important. Tough to choose one. I would like to answer it on my personal grounds. I think 'overcoming failure' is what I've learnt and used most number of times in other fields with ease.

In sports, there are hurdles to get over, much like in life. Sometimes things can surprise you or catch you off guard. They say life is not about what happens to you, but how you deal with it. And I always remember this.