It empowers you to draw necessary boundaries with people that will allow you to get your needs met in relationships without alienating others and without letting resentment and anger creep in.

Being factual about what you don't like in someone's behavior (without overdramatizing) is an important start. 

• Make sure your body reflects confidence: stand up straight, look people in the eye, and relax.
• Use a firm, but pleasant, tone.
• Don’t assume you know what the other person’s motives are, especially if you think they’re negative.
• When in a discussion, don’t forget to li...

A sentence starting with “You...” comes off as more of a judgment or an attack and puts people on the defensive.

A great formula that puts it all together: “When you [their behavior], I feel [your feelings].”

... especially when it comes to things you don't like.