I’m determined to get good at this.
During every practise session of an hour or longer, there will be 10-20 minutes ‘cold time’ and this makes no consideration for how “purposeful” the practise session is. Nor does it take into consideration how invested you are in what you’re actually doing.
However this also doesn’t take into consideration towards other time spent towards developing. Time invested in studying technique, music, researching, learning will ultimately be beneficial.