That happened to me with a cute little pet that was in his 30s when I accidentally killed him with an overdose. I wasn't happy at all when that happened and I put the game away for several days. I decided not to quit playing, though, and kept interviewing different pets until I found one that was just as cute (maybe even a little cuter). I was a lot more careful with the medicine after that, and I've raised two pets through old age and into their second lives already (on different Palm devices). Both of them are still going strong and I'm hoping they love me enough to want to keep coming back.