it depends on your relationship.. if you just dated and it never got deep, friendship is possible.. but if there was a deep relationship, even marriage, then pain comes with that when the breakup happens..
I have seen it happen when friendship can be there after.. but most often it doesn't happen.
I am civil to my first husband because we do have children and he may answer the phone when I call.....I try to remind myself when I hear his voice not of the horrible things he did to me, but the human side of him I can remember with almost fondness. It helps a little so I am not snotty to him.. now my recent ex husband.. there is NOTHING to say between us. He said he wanted to still be friends, but that was a lie. I didn't believe it for a second.. I told him when he left to get out of my life. Once he signed the divorce papers I told him to never contact me again or I'd get a restraining order. (there was harrasment in between to deserve that comment)..