Problems... Fiction is predicated on problems. Only I, being perverse, like to think of the word being challenges. I think this is because I grew up in the 1960s when The Problem Novel became a Thing. I didn't like that thing. (Still don't.) I wanted stories about people and ideas, not problems. People with problems... fine but the characters and story had to come first.
Okay, so my stories have challenges for the characters. I'm going to look at the challenges faced by characters in some of my books... starting tomorrow.