If a piece has 1000 notes, and 5 of them are out-of-place, it can ruin the whole thing.
You want a piece of music to be perfect. No blemishes. Nothing stands out or seems out-of-place. Everything is perfectly legato, or staccato, or whatever. A perfectly uniform touch.
Most teachers will tell you to work extra hard on those 5 notes. Put them in place.
Sounds reasonable. After all, there are only 5 of them.
But, what is it costing you to make those other 995 seem perfect? Is your goal perfection, or is it evenness?
Instead of trying to perfect every single note, take a step back and look at the thing as a whole. Make it internally consistent.
Don’t compare note #468 to the way you played note #468 yesterday, or the way your teacher told you to play note #468.
Instead, compare it to notes #460-#475. Just make it fit in.
And if it doesn’t, oh well. By the time you realize it, you’re in the 500’s, anyway.