There are two very different types of mistakes you can make in performance.
First is the kind everyone makes, no matter how prepared. It’s easy to have a slight slip of focus that leads to an error, but it’s just as easy to pick up from it. This kind of error is no problem – it’s momentary. It happens for a moment and it happens in a moment. We should forgive these mistakes without question. Even the best performers never reach 100% in any given performance.
The second kind of mistake you make doesn’t actually happen during the performance, though that’s where the outcome is heard. This mistake was made days, or weeks before, when insufficient preparation was done. The error during the performance is the result of not knowing how to perform the music correctly. This is the mistake that requires teaching after the fact, and reminders ahead of time. This is the mistake that is harder to simply forgive.
Consider your last performance. Can you identify the mistakes you made? Can you determine which of the two varieties they are?