At one 48 hour team race I was in, one of strongest guys had hardly ridden a bike. He was understandably nervous on the faster bits but working like a trojan up the mountain in one stage. I dropped back to check two of our guys were doing ok (1 was injured, another, shall we say, anxious for a toilet stop). When I caught back up with the less experienced guy, he was making great progress upwards and it was only as I drew alongside him that I heard him saying, Thomas the Tank Engine style, "you can do it, you can do it" which it turns out was his personal mantra ....
How about "Do or do not. There is no try"