Practice Makes Perfect buffs too powerful

The issue isn't so much the strength of the buff, its that it is always a focus moodlet even when it says you are focused on creativity (or whatever I don't recall the exact text but it does say what you are focused on). My suggestions:

• It should give you the inspired/active/playful/etc moodlet that matches the activity you are doing. I can even see a new menu choice of "practice until perfect" so you choose the single task the sim will be doing for the duration, the benefit builds up a charge, and changing tasks before it is at 100% makes you start over. In other words, it should be an active trait, not something that simply happens.
•  If possible I would support it giving you a negative score to other moods emphasizing that your sim is only ready for mental (for example) tasks right now and everything else will be harder.
• Once generated, have the moodlets be sticky, fading out over time or adding a debuff cooldown period. Alternatively, you can actively use the tea brewer, a bath soak, etc. to remove it. The idea here is identical to how they become too exhausted/sore for another go on the weight machine until the next day, but if they get a massage that debuff goes away. 
• To keep it from being too overpowered, add a cooldown that cannot be bypassed so you can't ramp it up again for 48 hours or something like that.