Don't understand this....

I split with a guy a couple of months ago, we had been friends before the relationship part, but it just wasnt working for me, I just needed some space. I told him this but hoped we would remain friends. Anyway, I dont think he wanted to be just friends anymore because he stopped calling etc.

It was what I wanted - yet when I saw him today, with another woman, someone I hate (he knows why) I wasnt at all prepared for how Id feel. I know of course he's gonna move on and that but I feel really low now - I dont know whether Im mourning the loss of the friendship or what.

Why would you feel like this when you were the one that ended it, Ive never had this before - It makes no sense!!