Lamont Brewster said that he didn't want to hurt people when he started boxing. He was really hesitant to throw, get aggressive etc. One day he let go and started busting people up. You will likely do this too. Remember that the other guy is there to beat you up, if you hurt him- he won't hurt you. And do lots of wall sits, they increase testosterone. Remember; Lamont Brewster & Wall Sits
Post- breakfast hyperventilation would be a slightly better option, as another poster mentioned earlier.