As a trained therapist, I would say that Bushido Man is on the right track. If you both are interested in staying in the relationship you need to talk about what happened and how to avoid it happening in the future. As silly as it may sound, you need to establish rules for fighting. Ideally, you should stop the argument the moment one of you feels threatened or attacked and say that you will discuss the issue further after a specific amount of time has passed. Following this rule should keep you both from becoming overly angry during a fight. I also suggest avoiding the blame game. The issue is not who is at fault for the incident. The issue is developing a plan so that it doesn't happen again. As for using a karate move, you crossed a barrier and now feel incredibly guilty. I suggest two things. The first is to apologize to yourself. You sound like you let yourself down because you did something you didn't think you would ever do. Apologize to yourself and move on. Heck, you can even give yourself a punishment if you think it would help. (Nothing to serious though, something on the order of no dessert for a week would be appropriate) This brings me to my second suggestion. Learn from it! You know how this feels so learn to avoid it. Find out when you decided to cross that line to hit your fiance. I'd say that knowing how threatened you must feel in order to respond with an attack is an important thing for a martial artist to know. Know yourself, know your limits. Thats the best way to maintain control. I wish the best for you and your fiance and I believe you can work through this.