Our behaviors flow from whatever particular state we are in at the moment. When you look at your own life you will notice that you act different depending on what state you are in. If you feel depressed you may find yourself watching more tv, eating more, etc. When you feel really confident you may find yourself cleaning, exercising, etc.
When you become aware of this you can begin to influence your behaviors more because you can put your focus on changing your state rather than trying to control each behavior that happens in those states. Our states are created by two things, our physiology and our internal representations. Our physiology has the biggest effect and is the easiest to change. Specifically, I am referring to your posture, breathing, voice, and physical tension.
If you were to describe someone who was depressed you may say shoulders slouched, head down, shallow breathing, kind of quiet. The oppostie is true for someone who exudes confidence, they would be standing straight, head up, speaking more intensely.
Whenever you want to feel different the quickest and easiest way is to change your physiology. Straighten your posture, hold your head up, take a deep breath, and speak with more intensity. You will find that this works every time you do it. As you master your abillity to create your state you will find your behaviors changing naturally. If you want to change a habitual behavior use this information when you get to that time when you usually do this behavior and intentionally change your state and notice that you may want to act differently.