Try

They all said it couldn’t be done
but he said, “How do you know?”
You can’t win the race that’s not run
and you’ll never know till you “go.”
You’ll never know what you “could”
or find out all that you “can”
never saying “I won’t,” if you “would”
so at least you can say that you ran
for life is not something we “don’t,”
but rather in fact what we “do”
not enough to say that you “won’t”
not who stayed in the nest- but who “flew.”