Be fair to everybody.
Life is not fair. Other people are not always fair to you; most of the time, they are unfair.
But we should not give up on being fair to everybody. Why?
No one will thank you for being unfair. If you become unfair, people who are treated unfairly by you will curse you and try to retaliate against you—perhaps for the rest of their life.
It’s just unnecessary. It’s always NOT a good idea to incur someone’s hatred because it will come back to us sooner or later—especially when we have a tough time.
You may think vengeance is sweet. It certainly is, but it will come back. Never get upset when you are treated unfairly. Forget it and be fair to others. Don’t get trapped in an endless loop.