Day 29: Describe a time when a spell failed

This post is part of a 31 Days of Secular Witchcraft series in which I answer questions about my own personal views about magic and witchcraft.  I urge you to answer the same questions, found here, on your own blog.

Overall, I've had pretty good luck, but I don't usually reach too high when it comes to my spellwork.  I did a spell to heal my dog who got recurring UTIs.  It worked on the UTI he had that time, in conjunction with the conventional medicine he was prescribed, but they continued to come back, and we eventually put him to sleep later that year.  I am on the fence about whether the spell helped the first time because it definitely could have.  It also might have been a coincidence.  It definitely didn't cure him for all time.