If you feel shy, act friendly. If you feel sluggish, start moving! When you feel an unpleasant feeling, counteract it by behaving how you wish you felt. It's not easy, but it does work. :) Psychologist William James described this phenomenon: "Action seems to follow feeling, but really action and feeling go together; and by regulating the action, which is under the more direct control of the will, we can indirectly regulate the feeling, which is not."