Every time you play something badly you have given your body bad information. Every time you play something properly you have given your body good information. The more times you play a part well, the better it is going to sound next time! When practising scales play only groups of 4 or 5 notes. When learning new repertoire or revising old repertoire practise only groups of 4 or 5 notes at one given time. Accuracy is the key! (David Russell).