85% Success Learning Sweet Spot

When practicing or teaching a skill, set the difficulty so the learner gets about 85% of attempts correct and misses about 15%. Start with material that is already fairly familiar, then add a small amount of new challenge—roughly 10–20% harder—so the task stays demanding without becoming discouraging. This keeps practice in the sweet spot for learning: enough errors to drive adaptation, but not so many that progress stalls.