Well, this is an interesting one.
First of, let me just say that I think it's awesome that the two of you worked this one together. It speaks highly of both of you that you are able to sit down on this one together and be able to point out both of your flaws in this.
While I can't really add to much to what Martian said, I just want to stress the value of trying to see things from the other persons side. Also argue naked when you can. If you can stay pissed at someone while they are naked, you know you have something that needs to be worked on.
Really though, next time this happens, both of you stop, take a step back for a minute, and look at the other persons view. I mean really look. Don't take it as a break to figure out your next come back. Both of you are still pretty young. Be prepaired to face that the cause of some of these spats is that you are growing in diferent directions and you aren't as well of a fit as you used to be. Aside from that, all I can do is wish you luck.