I'm sorry. I work in a shelter and it's never easy. However, it's not fair to the public to adopt out a dog with a history of biting--it's both a danger and does the shelter a disservice, as people will associate it with aggressive dogs (whether that's fair or not).

Sometimes being kenneled in the shelter for a long time can bring on severe behavioral changes in a dog that are hard, if not impossible, to change. It helps me to remember that as a shelter worker making the decision to euthanize, that's it's not my fault. It's not the dog's fault. It's the fault of people who continue to think of pets as disposable items, who leave them tied up in yards without training or socialization, who don't spay/neuter, and who breed them for profit without care. Get mad at these people, be sad at this situation.

I know it doesn't make it any easier, but I hope it doesn't change your mind about volunteering. Our shelter couldn't do half the work it does without our volunteers, simple as that.