Hi Happyfeet, empty-nester here too!
I have two dds, (22 and 19). I knew it was going to hit me hard, this emptying of the nest that I had built, and feathered and nurtured and loved for 22 years. I was actually fearful of how I was going to feel when my youngest went to uni. When DD1 went, I was so proud of her for her achievements and the way she was going bravely off into the world, and I still had dd2 at home, but I was gutted the day I left her there for the first time.
It's actually making me cry writing this, and that was over three years ago! She has now finished uni and is a grown up and lives her own fab life, and we talk very often and see each other less often, but are beautifully close.
But the prospect of my dd2 leaving, and it all being over, the motherhood stuff, worried me. So, between me and my husband we hatched a plan in advance and somehow it sort of worked! We decided to have our own adventure, and move to somewhere we'd dreamed of living, by the sea! And basically we moved just before she started at uni.
This gave me something exciting of my own to be getting on with so my daughter could go off to uni, and I could know that I wasn't giving off too many any desperate vibes, as I was fairly focused on the move as well. I won't say any of it was easy, and I didn't entirely escape the empty nest syndrome thing, as I really suffer with it sometimes, I really do. I'm still getting used to not being a mumma what dd2 calls me on a daily basis. Now it is in spurts.
For me, it has been like a kind of grief for the loss of all that lovely mothering stuff we've been doing for all those years. Yes, I enjoy the freedom I have now and yes, I am pleased that my DDs are out there in the world spreading their wings, and yes I know that means I did my job well, but I miss them sometimes and it hurts like hell. But then, when I get an email/text/call from either of them, I see that it's not over, it's just different.
I am very lucky that our move to the sea, while being a bit further from the dds, has proved to be an absolute delight, so I do have other really good and new stuff in my life. It is just odd, getting used to this phase of motherhood.
I apologise for banging on about myself, it's just that your post resonated strongly and I just wanted to say maybe if you think of something you've always wanted to do and then do it, or make plans to do it, then perhaps you can distract yourself in some way? There is no escape though, I don't think. I think it is a perfectly natural sadness that comes at the end of an era.
It is also a sign of how much it has meant to you, bringing up your dd.
And, whatever age they are, they come back, they need advice, they teach you stuff, you still teach them stuff sometimes, and actually, YOU ARE STILL THEIR MOTHER. It's just different.
So sorry op, that I'm not being much help, but I do actually feel your pain.