Whatever this is.
In all seriousness, every pet has idiosyncrasies, some of which may be challenging health or behavior issues, which aren't always easy to solve. They are imperfect, like their human guardians. The key is finding the perfect pet for you.
And if I have one piece of advice for anyone considering adoption, it's this: Bring home not just the animal that fits into your lifestyle, because there will many of those from which to choose, but the one you fall in love with.
Not the one you feel most sorry for, nor the one you feel like you should adopt, nor the one someone at the shelter or rescue might be kind of pushing on you a little. (Unless, of course, one of those is also the one you can't imagine living without.) Because when problems do arise (and they will), the thing that's going to get you through, provided it's a get-throughable situation (and not all are, and that's okay), is love.