pacing is just how often you are punching and how many combos you are throwing. it's having "gears" in boxing. your not always going in first or fifth in a car and you can't in boxing either. usually the boxer that uses his energy more efficiently is the one that wins. thats means not missing punches, dancing around too much and doing damage with the punches you land. one of the easiest things to do as a novice boxer is to completely wear yourself out in the first couple of minutes and do next to no damage to the opponent, not because you can't punch just because your not landing "clean" punches.