Concept
Deliberate Practice
4 books in the library reach for this idea - each in its own way. When independent authors converge on one concept, it usually deserves attention.
Grit
How this book uses it: Focused, goal-oriented practice at the edge of your ability.
Peak
How this book uses it: Focused practice at the edge of ability, with immediate feedback, guided by expert knowledge. Not fun. Not easy. Highly effective.
Peak Performance
How this book uses it: Focused, uncomfortable work on specific weaknesses with immediate feedback. 30 min/day beats 3 hours unfocused.
So Good They Can't Ignore You
How this book uses it: Systematic stretching beyond current ability with immediate feedback. Schedule specific practice, not just more work.