I think the worst problems are the ones that make you feel the most powerless. Everyone has problems, some huge, some little, but we can almost always find something to do about them, and taking some action, any action, no matter how small, helps. When there is nothing you can think of to do, when your own fate, and that of someone you love, is out of your control, that is the hardest thing in the world. That's where the expression "impotent rage" comes from. When your happiness, and that of a child you love, appear to be in the hands of someone who shouldn't be allowed to keep a hamster, it's intolerable.