How relationships really work...?

My fiance and I have been together for over 8 years. When things are great, everything is fantastic, when things are bad....they're really bad, everything goes to the opposite end of the spectrum. Last night we got into a really bad argument and fight, he got in my face, started calling me names, and said a lot of hurtful things (which I don't know how I'm going to forgive) so I slapped him. It wasn't right, but I felt as if I was protecting myself with him getting right in my face. So his reaction, he grabbed my neck with both hands (not hard) and through me on the bed. After that we kind of argued for a bit more until he pleaded to be left alone, so we went our separate ways. By all means, I know this was not right and is very unhealthy, I want to know the truth about relationships though. Is this how couples fight sometimes? Growing up, my parents divorced when I was young, I never really saw them fighting, and I haven't really been in a serious relationship other than this one, so honestly, I'm not sure if this is the norm or not. Can relationships really thrive on fighting fairly....and what is that like? HA!