Not the one that could
Who showed up on the day. Not those who could have. Both physically, and mentally.
So, how do you do that?
Practice being in the moment. Practice sensing the current sensation, and experiencing it for what it is, not what it could be. Take a second to take it all in. Remind yourself that this chance given to you is the one and only, and as the one and only, it requires everything you can give.
Then when the moment arises, focus on the sensation.