The Thought Bubbles

OK, I've been through every page in this section hoping someone would already have explained this, but I just don't understand it. Never have. And I know a lot of you all do understand it, so maybe someone(s) can explain it to me. When a Sim has a thought bubble pop up and it has an image with a red "x" over it, does that mean that the Sim hates the person or object, or they're just temporarily angry/upset with the person or object? I've never been able to figure it out. How do you all know how to interpret the bubbles? I've looked through the Sims 2 booklet that came with my game, but nothing explains it in there, either.

Thanks.