The things you learn from sports - setting goals, being part of a team, confidence - that's invaluable. It's not about trophies and ribbons. It's about being on time for practice, accepting challenges and being fearful of the elements.
At 4, I joined a summer rec team called the Sugar Bears.
I started swimming when I was four because my brother wanted to join a swim team, and I wanted to do what he did. They said I had to be six, but if I could swim a lap, then I could participate. So I swam a lap, and the rest is history.
