In a way, this is correct. If you do something 100 times incorrectly, then you become expert in doing it wrong. To do things correctly and improve you most do it properly each time. One example of this involves foul shooting, where players make 40 in a row in practice and then shoot 20 out of 40 in a game. Of course, shooting 40 in a row while well rested doesn't help.
Many myths involve sport's mottos.
Every one I have heard is antithetical to common sense and coaching. You don't have to push kids or people to do more than they should on an athletic field. Kids, even adults, always do more than they should, not less. Kids will gladly break their necks at practice. Your job as a coach is to prevent them from doing so.