This weirds me out.
I had a full Mood bar for many days, following my Sim completing her LTW wish of being a CEO. It was a +75 Moodlet, but even when it dissipated, I still had the full mood bar. The only moodlet I had was a New Friend Moodlet for +20 Mood. When I went home, I got a Filthy Surroundings moodlet caused by a glitch: I couldn't see anything that would cause the moodlet. But, even with just a total of +5 mood, I still had the full mood bar. What could cause such a good, but undeserved thing?
I'm still a noob to The Sims series...