For every time you do it wrong; do it right twice.

Making mistakes (wrong notes; wrong rhythm; wrong bowing etc) during practice time just makes the process twice as long. This is a public service reminder for slow aware practice. For every brain cell impression made by playing the wrong note, you need the safety net of two brain cell impressions of playing the right note. I've had students keep a pile of pennies: one penny to a 2nd pile when you play it right, one back to the first pile when you play it wrong. It should really be two back when you play it wrong.