Honestly no teacher could cover all the possibilities of what are the mistakes one trader may make or how one trader will get disappointment in trading. Literally there are millions of variations.
When we are agreeing like losses are also part of trading, we also must admit that disappointments also part of trading. We must make use of disappointment for improving ourselves to make good decisions in future trades. When traders are failing to make use of those lessons from disappointments, they could never find improvement in their trading.