I learned that hard work pays off in the end. Also to work on my weaknesses and focus on my strengths. The latter made me more successful on the racing circuit and much more fun overall.
I learned, pretty early on, that the best bike is by no means an indication of how good the rider is...saw some great performances and finishes on really low end bicycles.
Perhaps my best learning moment was overtraining can really ruin a season...train hard and smart.