Probably Mentioned in the Past

What is it with ex's? Why is it when 2 people decide to part ways, whether it be friendly or not....suddenly it seems like 1 or both of them expect all their friends to choose between them, and 1 or both of them decides they must stop going to places where they might see the other, and 1 or both of them are totally incapable of even being cordial or polite to each other? My mother was married to my dad for about 6 years, and they've been divorced for about 30 years. She was married to my step-dad for about 6 years, and they've been divorced for about 20 years. She can't talk about either of them in a positive light after all these years. Jerk, bastard & asshole are frequent descriptions I've heard about them all these years. I mean...I understand if the parting of ways was horrible & hurtful, how you wouldn't want anything to do with the person....but what is the point of holding on to feelings of animosity for decades? At what point is it OK to just let go of the old hurts and just let the past be the past? I think about this because I realize....that every person I've dated....I have little or no contact with. Most of them do not speak well of me, and the few that I have seen off & on over the years, pretty much ignore me when we come across each other. Last night, I was at a party. I saw a woman I was friends with & had dated. We never got really serious with each other, mostly because we couldn't get our schedules to mesh. Our dating stopped about 18 months ago. When I saw her last night, she looked at me, and then just walked right past me. As she was almost past, I spoke up & said hello to her. The look she gave me, made it clear that I was definitely bothering her. My last serious love....she & I parted way a few months ago. I purposely didn't try to contact her for about a month after, because I wanted both of us to have time & space to start to heal. I did have her former house-mate let her know that if she wanted to talk to me, she could call or email me. After nearly 3 months, I attempted to contact her. I let her know that I was thinking of her, hoping that she was doing well, and that I missed talking to her. About 3 weeks ago, when I mass-mailed my address & number change out....she was part of that list. Much to my surprise, she contacted me & let me know that her life was going well & that she too was moving. I replied & let her know I was happy to hear from her, and that I looked forward to talking to her more. And.....nothing. Is this just the way love & relationships are? Do people just stop existing for each other when things go bad? Isn't there ever a chance for things to mellow out & they can, if not be friends, at least be cordial & polite to each other? Is it necessary to pointedly ignore each other, and to tell everyone how horribly the other person treated you, and to try to turn people against your former love?