Perhaps empathy could actually be helpful in this. Animals generally do not dwell on things which happened in the past. A dead animal is not suffering and an animal which has suffered in the past is certainly not thinking about it. They are living in the present. This is one of many lessons which we learn from spending time with them. The emotional upheaval you're suffering isn't really about the animal. It's you and your outlook.

Situations which are truly bad for animals are not usually not helpless. An animal who is suffering in the present can be assisted so that suffering ends. This may be through euthanasia or other more positive methods like rescue and veterinary care. You can and do have an effect in these animals' lives. There are positive sides to everything. Finding these can assist you in training and enriching their lives. Dwelling on the negative doesn't help you or them. In fact, animals often pick up on negative vibes and feel more uncertain as a result.

Unfortunately, shelters are often sad places. I commend those who can deal with their emotions and continue on in this environment. If you find that you can't deal with these feelings as they crop up and move on, then perhaps this kind of work is just too much for you. There are other ways to help animals, which are often more positive. Rescue work doesn't always have a happy ending, but it is a much happier and more proactive environment. No matter where you end up, the feeling that you're making a difference is often what gets people through the rough days. Work with this concept and your own outlook, then decide what's best for you and where you can truly do the most good.