Learn a Piece of Music You Have Been Putting Off

Practising a difficult piece from beginning to end produces slow progress on the hard sections and overconfidence in the easy ones. The practice method that works on a specific piece does the opposite: identifies the sections causing the most resistance, focuses on those first, and builds a routine that keeps momentum within the time available. This designs that routine for the piece and level in question.

I want to learn [piece of music and instrument] but every time I sit down to practise it I make slow progress and give up. Help me design a practice approach that: breaks the piece into the right units (not necessarily bar by bar), identifies the one section that is causing the most resistance and deals with it first, builds a practice routine of [available time per session and sessions per week], and tells me what good progress looks like for this type of piece at my level. I am [beginner / intermediate / returning to the instrument after a gap].