There's no shame in defense! You are a nice person; don't make one "act" into the whole of who you are. If you perceive someone is hurting/going to hurt you, defending yourself, even if it may hurt the other, is not a "bad" or immature thing. We only get our own lives here, not the other person's and we can't read minds or evaluate after the fact. We do have to do things to ensure our own survival and sometimes they don't come out "right" but that's how we learn and grow. You can't fix a mistake you don't make and you can't learn from a experience or lesson that isn't taught.