Yeah, you definitely don't wanna mess up the relationship you're in.
A big chunk of me still misses my ex, the one that had a breakdown, and finished with me to go sort himself out. Still hasn't and for a while he got back with his ex. I could have seen myself getting back with him until the ex was brought into the picture, oh and when I found out he started shagging round himself after he broke up with me. But, yes I agree that exs are exs for a reason.
On a slightly unrelated topic, I had him on the phone not that long ago, apparently his ex wife was on that webcam embarrassing bodies clinic TV show, talking about how her hubby (at the time) had a giant penis.... and she didn't tell him... Now everyone knows he has a large penis and he HATES it. Who knew, a lot of men with large penises actually aren't that confident about it!