How do I disconnect from my work?

Hi. I'm 22M. (JUST A FAIR WARNING, IF YOU ARE AGAINST ANIMAL TESTING, PLEASE DO NOT READ)

As you can see from the title, I'm just a little bit lost rn concerning my work. I work as a laboratory technician for a biomedical company, and we do a lot of great work that will no doubt help and possibly save hundreds, if not thousands, of people. The only thing is, I'm required to do euthanasia for my work on small animals, mainly mice and rats.

I can't say too much, but earlier today I messed up the stick and the mouse had a seizure because of something that I did, before I was able to administer the euthanasia solution, and I just feel really terrible. I thought that eventually it would be easier for me to do my work, but sometimes it is just impossible for me to not bring it back home with me.

I often cry while driving back from my work. I try to tell myself that it's for a greater cause (which, it really, really is. The work we are doing is amazing, and I truly believe that it could help thousands), but it is just getting really difficult for me to do so.

I was wondering if anyone has something like this? Like, maybe you're a nurse who has seen terrible things, or something like that? How do I detach myself from my work? How do I not feel like a horrible person for doing what I do? Any tips would be really helpful.