Bossybum, I have had lots of firsthand experience with having horses taken right out from under my nose. It has happened to me four times, and yes, it is sad and very hard, because naturally you grow close to the horse. But I just had to accept it and move on, because none of them belonged to me and I had no say about where they should be and what should be done with them.
I don't think it is confidence. I think that it's rather just that you were let down, and you didn't cope very well with it. I suggest that you try and get back into the flow of things and try to form some kind of protective "shell", because sadly, things work like that in the horse world. I hope that things get better for you, and that you can get back to riding and being with horses again.