I admit that it's tough, and I was a "foster failure" when I got into fostering and socializing dogs that had been abandoned. My first wife was actually the failure, she couldn't bear to let go of this beautiful German Shepherd female we had been tasked with. Bridget was the first one we fostered, and I know that I could easily have been persuaded to keep a few of the later ones, but the idea was to make them adoptable. We saved many lives, us and our own dogs, by showing the foster dogs that they didn't have to fear people and by training them in basic commands and manners. Hard as it was to return them to be adopted, it was so much more rewarding to know that they had found a good home.