The last time someone proposed to me - I said no. Not because I was rejecting him - but because I didn't want to be married again. He popped the question on Valentine's Day at a very posh restarant in front of the whole room - on his knee. I told him yes publically - because I'm not a total bitch but when we got home a serious discussion ensued as to whether he really wanted to get married or if we were just doing what we had been doing with better jewelry. We already owned a house together - I figured that was a pretty big commitment and I should get 'credit' for that. But he was determined to make it 'legal' which was irritating because we had previously discussed that I didn't want to get married again. In the end, I had a full blown anxiety attack and needless to say the engagement was off. He moved out by June of that same year - we were officially no longer a couple by April.
Interestingly enough - my current SO (also My Best Friend - BTW) has no interest in getting married again. He's a widower. And also no interest in moving in with me. He lives in NY - 700 miles from my front step.
And we both couldn't be happier. :)