When learning to perform a piece of music, it is useful to work a little a time. Each measure or even note could be a useful unit to practice.
However far I would make it into practice, my piano teacher of years back would suggest, “end on one”. By this, she would mean that when I was to end a practice session:
When wrapping up a session of work, it is often useful to consider:
Whatever that next action is, it can be useful as a task, making for an excellent bookmark.
By coming up with a clear next action as a final act in a session, we can return to the work with solid footing, ready to go. And, we better clear our mind of the current work so that we have more mental resources for whatever else we may wish to do.
For an in-depth exploration consider Being Productive - Simple Steps to Calm Focus Module 10.