A mother's dilemma

When my 21 year old son told me he was bringing his girlfriend of a few months home for Thanksgiving I didn't give it a second thought. He is my only child and he has lived 750 miles away for over two years. I don't care if he brings Godzilla home with him just as long as he gets himself here.

I assumed that the new girlfriend would be smart because he likes smart girls. I assumed that she would be pretty because he likes pretty girls. And so on. What I didn't assume was that I would like this young woman as much as I do. She is accomplished, brilliant, funny, talented, beautiful, adorable, interesting, and kind.

They are very young, they are in colleges that are 6 hours apart. They both want to travel when they get out of school. I have no right to think that this will last.

So how are mothers supposed to keep from getting too attached to their children's significant others? What if she dumps him? I don't want my heart broken for me and for him. What if he dumps her? I don't want to have my heart broken for me and for her. While I think I have appropriate boundaries in most personal relationships, this one baffles me.