It's not easy to do that. You have to work on it. First you have to know the meaning of stress. Anything which is not in accordance with your "self", could cause anxiety for you; and you sense this feeling as stress. Second, find the reason(s) that cause stress for you. Sometimes you can change or modify the cause, sometimes you can't. If you can't, the result will be "chronic stress" which is the worst thing for your body and soul.