Moon Logic - Is Key Learning Mystery Cache

Here is the original puzzle: IS KEY LEARNING.
This puzzle is not placed at the correct solution to the above puzzle.
This is the "Moon Logic" solution-version.
A discussion of the puzzle can be found here in this GBA thread: Venona 2012 "Is Key Learning"

When I google "The key to learning is", here is what I get - in order - on my first page of results:

• important in every stage of life
• eternal repetition (NOTE: this is the correct answer)
• work - effort, diligence, and industry
• listening to the teacher
• practice
• to make the time to learn
• a good night's sleep
• in your own brain.