“...we’ll take it one day at a time...”
Taking one day at a time means you flub it one day (or one minute) and you have a new chance the next day (or next minute) to go at it again.
Granted, some sports require that attitude more than others. A goalie IS going to get scored on every game usually, a pitcher is going to throw a home-run ball most games, etc. They need to be able to shrug those off and move on quickly.
But even a flub in a sport like gymnastics where they are nearly perfect all the time - well, you have to move on and “take it day by day”. Not give up in the middle of what to many is the biggest sporting event they will ever be in. Especially in the team event. What a loser.
I think the truly great ones, across all sports and eras, are able to shrug off their defeats - or screw-ups - quickly and totally and move on to bigger and better things. I am not knocking those who are competitively destroyed by one devastating loss or performance. That is after all why the great champions - Nicklaus, Brady, Federer, et al - are so rare.
I read an interview with Arnold Palmer. He won only one US Open - no shame there, one US Open would be a career for many golfers - but was so close so many other times and never closed it out. He said it was so hard to maintain that indescribable edge necessary for world-class high-level competition, and you never knew how or when you could lose it forever.