Learn from the past, but don't live there. Build on what you know so that you don't repeat mistakes.
Worrying about the past or the future isn't productive. When you start chastising yourself for past mistakes, or seeing disaster around every corner, stop and take a breath and ask yourself what you can do right now to succeed.
A string of successes can kill you if they make you think, 'Hey, I'm smart; I can't make any mistakes'.
Expect to make some mistakes when you try new and different approaches. Sometimes colossal failures lead to spectacular successes.
One mistake will never kill you. The same mistake over and over again will.
Remember you're not entitled to anything. You have to earn your success every day, and you will make mistakes like everyone else.
An optimist understands that life can be a bumpy road, but at least it is leading somewhere. They learn from mistakes and failures, and are not afraid to fail again.