This is a fascinating snippet from Anatomy In Motion about how muscle memory works.
In brief, your body learns movement patterns both from doing things right and from judging how you are doing them wrong.
Plus you need to alter your practice patterns frequently so that the brain gets better at laying down this muscle memory and making quick right/wrong judgements.
A good explanation for why we constantly vary our exercises in Pilates, even though the nature of each exercise is very similar. And an excuse for us teachers to continue to critique your movements!