This has never happened to me, and I did a lot of casual dating for a few years there. For what it's worth, only one woman ever seemed really sad about breaking up with me, and that was the only one that I ever proposed to.
I'm thinking that it must be something that you're doing. I don't think that it's the type of woman that you're seeing, because I dated a lot of different women back in the day, and never saw the kind of breakdown that you've described. Or maybe you're just a really cool, good-looking guy, so that raises the stakes for these women and they get more emotional quickly. I dunno. I look like my avatar, only a few years older now, but I just don't seem to inspire breakdowns.
Good decisions come from experience. Experience comes from bad decisions.