Yes I agree that having serious relationships with other people teaches us about what we need in a partner, what we're willing to compromise on etc, so staying single hoping to meet 'the one' is pointless, because once you meet them you may not be ready for a proper relationship.
DP & I are both very different partners to each other than we were to our former spouses, mainly because we were both reacting to be treated a certain way, but also because the baggage we carry now makes us a bit more thoughtful about each other.
I am able to say that 'x' was a deal breaker with ex and so I will not tolerate even a sniff of it in this relationship. He has admitted that he was selfish in the past and is doing his utmost to notice and correct this behaviour with me, whereas he perhaps didn't realise (or care) with his ex that he was being self-centred, but with me he doesn't want to be 'that person'.
I think just having that willingness to 'be better' for each other makes us well suited, but I also believe that a lot of it is the sexual chemistry which binds us, the feeling that we fit, that he 'gets me'.
Like Annakin, I have a very physical reaction to DP's words and just looking at him does strange things to me, so I feel like there must be something specific about the combination of me and him that is special.
I felt it from the first time I met him, although I admit I was in quite a vulnerable state at that point, not long out of a 13 year marriage, with a few dates under my belt, so I was eager for some affection. I certainly haven't felt this way with anyone before, not even XH in the early days, but then I was a different person with different needs and experiences before, so whether I would find that easily with anyone else now, I can't say and hope I don't have to try