This is a quote that a lot of people have trouble with. Especially those people who have a tendency to blame themselves and treat themselves too harshly whenever they make a mistake. Generally, people who treat themselves to harshly also treat others the same way with high expectations.
When you beat yourself and waste your time whenever you make a mistake is it really, truly worth it? Of course not! We are human, believe it or not, no matter how high your self-expectations are! Life is too short to beat up yourself over past mistakes and regrets. Just learn from it and move on. If it can be fixed, fix it. If it cannot be fixed then accept it. Otherwise, it is just a waste of time.