I was relatively perfectionist as a kid, and it was one thing that led to the mutual frustration of/with my teacher and giving up formal piano.

Now I'm much more lax in most areas of life, guess I found too tiring ;-) to aspire for perfection in everything...

Martha Beth Lewis has many good points on many piano topics (and not only piano).

I agree, for that kind of learner, as specific technical *feedback* as possible (WHAT really happened / is seen from outside, HOW to do better, maybe WHY it happened, WHAT other variants are if first way fails) is much better than just criticism (The perfectionist is already better at self-criticism than at really doing it ;-)).