Mistakes are the best teachers. One does not learn from success. It is desirable to learn vicariously from other people's failures, but it gets much more firmly seared in when they are your own.

This quote means that it is easier to learn from failure than from success. When we fail at something, it is often a more memorable and useful lesson than when we succeed. We may be able to study and learn from other people’s mistakes, but if we make our own mistakes, we are more likely to remember them. Thus, mistakes are a great way to learn and grow.