A basic but yet very effective exercise is the push-up.

Push ups a basic but effective body weight exercise

When it comes to using your own body-weight, the push-up is probably a exercise that everyone has done.

On the upside is that you can do it pretty much anywhere, if you feel tired, drop to the floor, or ground, and do 10-15 push ups, chances are you will feel more energized after.

By raising your pulse, you change your current state, if you feel a urge for a chocolate bar, try do 3X20 push ups, chances are you feel so much better now, that the chocolate bar is not so hard to resist anymore.

And the best thing is that you only need yourself, and some type of surface to perform it on.