If your Mars is in Libra
You'll argue someone else's case better than your own. Fairness fires you up, and you'd rather win with charm and strategy than with force. Going after what you want for yourself is harder, since you can weigh every side until the moment has passed. What makes you angry may go unsaid, then slip out later in a sigh or a sharp little joke. You can say no kindly and still mean it.
Don't know your Mars sign? In most cases, your birth date is all you need to look it up.