FoPP 014 1.II.6 Shortening Difficult Passages: Segmental (Bar-by-Bar) Practice
Fundamentals of Piano Practice - A podcast by Chuang C. Chang / Henrik Pantle

A most important learning trick is to choose a short practice segment. This trick has perhaps the largest effect on reducing the practice time because of many reasons ... http://www.pianofundamentals.com/book/en/1.II.6