http://tinyurl.com/67bygfs
You can't control others’ acts, but you can control your reaction to their acts, and that is what counts most to you."

No one can make you feel any negative emotion -- fear, anger, or inferiority -- without your express permission. There will always be people who find perverse enjoyment in upsetting others, or who simply play upon your emotions so that they can use you for their own selfish purposes. Whether or not they are successful depends entirely upon you and how you react to their negative behaviors. When you are forced to deal with such people, recognize from the outset that they are trying to upset you, not because of something you may have done to them, but because of some problem they have with themselves. Tell yourself, "This isn't about me. I will not allow this person to upset me. I am in control of my emotions and my life."