Sorry you're feeling down.
I don't know that it will help, but I'll reiterate what Tin said earlier. I'm 30, and I still need my mom. And I'm still close enough to 21 to remember vividly that I
definitely still needed her at that age! It's not the same kind of need that I had when I was 12, or 5, or an infant... but it was still really important.
I'm sure it's not an easy adjustment to make, but one thing you can perhaps look forward to is that, at this age, your daughter may occasionally start telling
you "Mother, I can now not only sympathize, I can empathize as well. I love you." And I know my own mother never gets tired of saying "I told you so!"