Cats can be moody just like people. The only difference is that when people are moody, they can communicate (sort of) their feelings. On the other hand, cats can’t speak so they need other ways to communicate their feelings.
Purring is a common way cats express contentment. Also rubbing against you is another way to show their affection. Perhaps the best way to measure your cat’s mood is to look at its tail. the tail can swish back and forth to show contentment or annoyance, but it will definitely reveal your cat’s mood. Now you just have to figure out what it means.