I've done something extremely stupid and become very attached to daughter's boyfiend

[SillyBillyMother]

And she's broken up with him.
He's completely delightful. DH and I are as bad as each other and feel very sad about it.
She is the first of DC to have a serious relationship and he will no doubt be the first of many. It's a hard one, and an important lesson, I'm pretty sure he's feeling really sad.
I'm sad because we won't have him around anymore, I won't feel that lovely sense of safety from knowing someone is taking care of her, I'm sad thinking of him being heartbroken and if I really interrogate it, I'm reminded of losing my first love.....
I wouldn't be a teenager again for all the tea in China.

I'm not sure that's what the OP meant. I suspect it was that the bf was a nice, caring chap; and who doesn't want their dd to be with someone like that?

bless you. best you can do is let them be. things may change

I think you sound lovely OP, and your DD seems brilliant.

I think your feelings make sense - and are a recognition of the good choice your DD made in her first boyfriend!

I married a twat. Then dumped him. When I met and married DH, my dad said he could finally relax. I KNOW I can take care of myself and did. But my dad just wanted to feel someone else loved me.

Be kind to yourself.