Slipping through my fingers (or learning to let go)

This morning my big girl left at 6 AM on a school trip: 5 days ponytrekking in Wales.
Back in November, when the form came through about the various school trips, she was instantly drawn to this one, but was a bit tearful when she realised that she would not be able to speak to either me or J. for 5 days. She has never been away from either of us before and normally speaks to one of us in the evening if she's staying with the other one.
She agreed to try and get a place anyway and take it from there. Well, she did get a place and from then on, she only got more and more excited. We found some secondhand jodhpurs and riding boots, we bought her a new rainjacket, she had her bag ready at the beginning of last week. I had to say goodbye to her on Saturday afternoon as she was staying with J. this weekend and he was taking her in this morning. He rang at 6 to say she'd gone off fine, all smiles and waves and giggles with her friends.

It is very strange to suddenly hand responsibility for your child over to five people who I've never even met. It is very strange to see your daughter be all excited about a trip that doesn't involve you at all. She's growing up very quickly and becoming more independent all the time. I guess that's the aim of parenting: bringing your child up to become an independent, happy human being. And I'm very proud of her for going off so confidently.
But personally, I feel I'm always behind one step. It's a cliché but it does seem like only yesterday when she was a baby. I know she's going to have a great time and I wouldn't want it any other way, but boy does the house suddenly seem empty without her.