Learn from your mistakes and the mistakes of others.
My father recently reminded me of something my grandfather said about business owners. He said that there were three types: The first make mistakes and repeat them. The second type, which represents the majority of business people, make mistakes and learn from them. They do not repeat them. The third type represents the best business owners.
They learn from the mistakes of others and never make those mistakes. Yes, they make some mistakes. However, they don't make those made by others.