My family has been fostering for a couple of years. You love them while they are there and then when they are going you tell yourself they are going to a good permanent home and if you were to adopt them you couldn't foster any more. That makes it ok. My family has only had a couple of problems letting go (with the exception of my 10 year old sister who wants to keep them all).
We had one pair Biscuit and Triscuit. Triscuit was adopted within a couple of weeks, but we had Biscuit for months, she was hard to let go. It hurts because The woman who adopted her put her on a run which she escaped and came back, and the next day the woman put her on the same run, and she didn't come back. There was a lot of construction in the area where she lived so we think a worker found her took her in and fell in love with her.
The other pair was Paris and Tyler (See "The Herd" post for pics). It was harder on me than anyone else in my family. We had them a total of 3 times, and for a while each time. I love them almost as much as I do my own dogs, they were hard for me to let go.
Those are the only problems letting go we've had and I've lost count of how many dogs we've had, I think it is something between 30 and 50. If you can get through those first few dogs, it becomes easier. You love each one, but you learn that they will be well taken care of.
