What really fascinated me about this was how differently people feel about these things, particularly the priorities. Even the most basic survival needs vary; one person may care a great deal about sleep, but not worry much about food; another may scant sleep but fixate on food. The whole thing came up when I was studying Calliope and Vagary. The real reason they keep butting heads? It's not just that they're a superhera and a supervillain, or stuck in an awkward relationship. It's that their needs have very little overlap. When their goals for survival, sanity, and comfort are opposed then they keep getting in each other's way.
It's a very illuminating character exercise to go through and mark what people's different needs are.