You only have to be right a few times in your life to make your career. Most people are right zero times, and hardly anyone is right 10 times. Von Neumann might

You only have to be right a few times in your life to make your career. Most people are right zero times, and hardly anyone is right 10 times. Von Neumann might have hit 10. So regretting past mistakes is a big waste of time. Learn from them, but don't let it get to you emotionally. (All easy advice to give, and hard to follow.)