It has been said in the previous chapter In what way and how often you should practice? Regular practising on a daily basis is essential for progress.
It is most important that you want to solve specific technical, musical or sound problems, and it requires great patience.
If you do not practice regularly and correctly, there will be no results. If you are “losing” time to work, “lose” it properly!
You should analyze each problem that is difficult to solve and repeat playing slowly countless times (perhaps countless days) with gradual increase of playing speed (tempo). Do this in order to become aware of each tone you have played and you should gain control of your instrument when playing faster (later the fastest). The Latin proverb says: Repetition is the mother of learning.
Every new etude or piece should first be well practiced, without slurs and dynamic signs. Only when you have learned the exercises, add the slurs. Add dynamics in the end when all the previous problems have been solved.
Taken from my book