A child praised only for speed may experience carefulness as decline.

If speed is what gets praised, slowing down feels like getting worse. The child who was quick learns that the quickness was the achievement, so as the material gets harder and demands care, the necessary shift to working slowly registers as failure. They abandon exactly the habit that would carry them further.

Praise the checking, the second attempt, the noticing of an error. With yourself as well, if you were fast early. Careful is not the decline of quick, it is the next skill, and nobody tells the people who never needed it.