Ever heard the term "Step into their shoes,"?
How about the Golden Rule?
I know you're probably like: "Not this lesson again!" But it is a very important one that will help you throughout life.
When you are in a situation, an argument, a fight or making a decision imagine what it would be like from the other person's perspective. That way, you can avoid hurting another person's feelings.
You are not the only living creature in the world. Other people, and biotic beings, have feelings too. You should always consider other's feelings before making an action.
This way, it is easier to make friends who are always happy and comfortable being around you.