Terribly attached to them and too much for my own good sometimes. The bond I have with my horse is unmatched for me. I know someone people say what they feel for their dogs and small pets is the same, but not for me - no where near the same.
I have sold horses in the past - I sold 4 - all at the same time in my late teens when I was emigrating abroad. I kept my mare and she went out on loan and the rest of them I sold. I knew it was coming and I think I'd managed to detach myself somewhat before hand (plus I'd been abroad for most of the summer with someone else looking after them). So when I came to sell, it wasn't quite as bad (and I needed the money.. there was no way i could keep 5 horses while I was living abroad!)
Two have since been PTS and it really upset me on both occasions. I felt INCREDIBLY guilty as though, if I'd kept them, it might not have happened.
My current boy will never ever be sold. We're in the process of moving abroad yet again and there was no question this time of him going with me. Ultimate plan is to emigrate to New Zealand in a few years and again, he'll go with us - regardless of the costs involved.
Sometimes you have to sell.... but I do everything I can now to avoid it because its a harrowing experience.