more on habit
Depending on the natural inclination and passion of the student, keeping what's naturally expressive is important in the midst of working on improving technique. A habit can seem 'natural' when in reality it is a reflex or a reaction to a set of certain physical-psychological balances. Then during the repetition of the action, can turn into a 'hardened' habit which sometimes people call their 'second' nature.
A fall back situation, (habitual- comfort- zone) are often seen and felt as 'second' nature. A natural inclination towards needing and/or wanting to express oneself, (on an instrument and in other areas of life probably as well), most often will not get lost while working on refining and developing more technical control. BUT, if the student has a teacher that has an extremely tight and narrow idea of how an instrument or piece 'should' be played, it can interfere with the natural talent and become very destructive to the student who needs to express themselves personally in their music making.
This is why, in my view, working on technique needs to have at least the prime element of music involved which is movement. Not just metronomic mono rhythm, but fluid directional movement. Then the expressive player can channel the energy into that movement and find it's musical substance even if the 'spirit' of the exercise is on the drier side. It can still have grace, momentum, vibrancy and other qualities. That is why I often think of being an actor that has many modes of behavior when I play. When doing that, my playing always is energized whether it is an Arban's study, a dry staccato Stravinsky note, an excerpt or a prayer. It's all in the connection.