2 - The key to productive practice -- Spaced repetition

I cannot guess "productive practice" means. Learn to play piano is not manufacture something. But I have one idea relating to the word of "productive".

If you practice too much, you may ruin a couple of day because of the pain at your elbow. In training your fingers, you'd better realize that your little finger and ring finger are there to hold things. Their function were not defined to strike something.

Thereby if you work on those two fingers, your elbow starts to overwork and may accumulate some heat. It's like the shoulder of baseball pitcher. If you pitch too much, your shoulder gets sore.

Then you need to plan your practice. 15 minutes in the morning and evening would be best. It totals to 30 minutes, but you never try to practice 30 minutes consecutively. It easily hurt your elbow, and thereby it can't be productive in a long run.