Fun question, I think--are 10's always a 10, or is that happiness number fluid ? If it's not always a 10, does that mean it never was a 10? Hmm, thankfully there are other world problems to ponder. But it speaks to whether it is realistic to think every item must be perfect all the time.
I agree with mood and situation.
--Confidence for certain situations or people may vary.
--New people and situations may bring up new issues
--Moods are moods--they'll pass, but they're there when they're there
--Experimentation may involve risking confidence ( comfort/safe zone). Might be a bust or might be something my "eye" adapts to.
I have actually labelled a few items that I nearly tossed out, but then realized they worked in specific situations/outfits--so I learned not to bother with them on certain days but identified the specific niche for them. This is part of what I mean by moods will pass--you don't have to change your life or your closet over a mood.
I do try to pay attention to things that consistently don't "work"--then that means there are not enough situations/moods to justify the space and energy.
If I put something on and then leave it on the floor in a mad dash of changing, over and over, then it's either too something or not enough something.
If something just feels great every time you put it on, on any day, for weeks or months, then that's worth duplicating (either exactly, or its essence) !