I once had three mice. I named them Theodore, Buttercup, and The Holy Spirit. They were feeder mice meant to be fed to snakes. I had them for about 6 months and they helped with my depression. Mice are particularly hard to pet, and they started to hiss and bite at me whenever I went to feed them in the cage. This went on for awhile and on one particularly bad day I decided to kill them off. I rationalized that they were feeder mice that were going to die anyway. I took a half empty jar of peanut butter and put then waited awhile before I put the lid on it.
I woke up the next day feeling the absolute worst, and I was worried that my family would come in and notice that my mice were missing. I bought three more mice and pretended that everything was fine, but in the back of my mind I felt that there was an aura of fear left behind by the previous trio and these new mice knew that I was a mouse killer. I kept them until I left to find myself across the US and I couldn't find anyone to take care of them and I didn't have any friends with snakes so I decided to kill them in the same way, in a peanut butter jar.
I don't trust myself to take care of pets or plants right now. If you buy a succulent I'll buy a succulent.