A few weeks ago I was showing the movie the movie Peaceful Warrior
to a friend, and a quote really stood out this time, that has a lot to do with not being attached to the outcome:
"You don't surrender your dreams, Dan. You surrender the one thing you never have and you never will: control. Accept that don't control what will happen to you. That you may, or you may not compete in the Olympics... That you may, or you may not. And that you're something exceptional either way."
I've been practicing this lately and it really seems to help: whenever I find myself drifting off imagining a desired outcome, or getting nervous about it, I repeat that line to myself.