There can never be enough reminders: Practice does not make perfect.
I can never say enough: Practice makes permanent.
I'm so glad that someone decided to adjust that silly little axiom to say something vastly more accurate. The original wording is so wrong, so misguided, that I dare not repeat it verbatim.
We all need reminders that practice time brings us no closer to perfection or artistic or technical mastery. Practicing only reinforces what we're doing, good habits or bad habits.
It's worth noting though, when we have young kids that we're teaching, they can't innately comprehend the difference. It is so important that we help students and give them tools to make good habits permanent in their practicing. We see students for 30 or 60 minutes once per week (most of the time). They practice more than that at home and need to be able to work independent of a talented teacher.
But, one thing that Suzuki piano training has taught me, is that we have a secret weapon at our disposal: parents. If my student's parent understands good habit-forming practice skills, they can guide their student at home. Parents need not be able to play piano, but there are innumerable things they can do to help their kids practice better.
Parents can listen for balance between the hands. Parents can listen for a steady tempo. Parents can listen for hiccups in continuity. Parents can listen for an ugly note. Parents can listen for crescendos or decrescendos. Parents can listen for false accents.
As long as you give them a specific item to listen for in one specific spot, parents can go a long way to helping students make permanent, good, habits in their practicing.
"Modern performers seem to regard their performances as texts rather than acts, and to prepare for them with the same goal as present-day textual editors: to clear away accretions. Not that this is not a laudable and necessary step; but what is an ultimate step for an editor should be only a first step for a performer, as the very temporal relationship between the functions of editing and performing already suggests." -Richard Taruskin, Text and Act