Old saying meaning today: The past is the past, you can't change it. Why worry about something that is no longer in your control? Focus on what you still can do, not in what's finished.
“I always did something I was a little not ready to do. I think that’s how you grow. When there’s that moment of ‘Wow, I’m not really sure I can do this,’ and you push through those moments, that’s when you have a breakthrough.” ~~ Marissa Mayer