Whether it was because Nick was the second child and striving for attention, or because he didn't want to let his parents down, I don't know. All that I do know for certain is that inside of Nick was a burning desire that would not let him settle for less than the best. Being average was something that Nick never considered.
This book is a compilation of everything that he thought about while overcoming obstacles in pursuit of his goals, athletics, and in life afterwards. If you are satisfied going through life being average, when you are older, you will only have average memories. Push yourself. The pain and sweat required to be the best is nothing compared to the memories you will have provided for yourself.