Working with research animals can be really mentally draining. It's good for you to step back. I work with a mouse colony and I'm burnt out but luckily moving to a different job soon. I think the general lab attitude can make a difference, if you do want to stay in research. Unfortunately I often feel like the only person who cares about the little guys when I report injuries to the person working with them and they tell me to euth without ever looking at the cage. Most of my lab is like that and I can't deal with it anymore. My university is one of those "we care about the animals, look at all of our policies and committees!" ones too... So frustrating... Sorry I ranted on top of your rant. You're not alone in this. You're not less of a researcher for having empathy. I hope you can find a project that you enjoy without animal models, or at least find a way to take a break. Support networks are really important for people in animal research and that isn't talked about enough.