In rock climbing we say, commit to the move. It means that once you have decided to do the move / sequence, then cast off and do it without any doubts - no second guessing yourself - mentally and/or physically.
The second you start thinking about failure is usually when you blow the move and fall (hopefully, you're not soloing).
I think commit to the move also applies to cycling, especially while zipping through traffic at high speeds, riding some rough singletrack and definitively racing.
So once you have decided that you are going, then go.
It ain't no use to sit and wonder why, babe
It don't matter, anyhow
An' it ain't no use to sit and wonder why, babe
If you don't know by now
When your rooster crows at the break of dawn
Look out your window and I'll be gone
You're the reason I'm trav'lin' on
Don't think twice, it's all right