Moodlets are tabs that appear in your Sim Panel, marking what actions or environmental features are affecting your Sim’s Mood. Moodlets last for a predetermined length of time, or remain for as long as your Sim is close to an environmental feature. Moodlets add up Emotion points, and the most points will set your Sim’s Mood.
Knowing how to trigger positive Moodlets, and how to remove or lessen negative Moodlets, is the key to keeping your Sim in a positive Mood. For example, nicely decorating your home will give passive Happiness bonuses to your Household, while cleaning up messes in your home will lessen the time your Sim feels Uncomfortable. Actions can either add Moodlets (brushing your teeth, for example, gives a boost to confidence) or lessen the time a Moodlet lasts (such as taking a bath while your Sim is Sore).