Lesson 1 :  If someone has cheated or embarrassed you, you are not allowed to tell others about it. Although you might claim that your sole intention is to disgrace the wrongdoer, your personal involvement will influence you to be motivated by the desire for revenge.

 

Lesson 2 :  When someone refuses to do you a favor, you are not allowed to mention that to others. This would include instances where the person did not lend you money, give you charity, invite you to their house, or greet you in a pleasant manner. Mentioning your annoyance is considered lashon hora.