This is perhaps the most important quote which no serious student can deny. Mains is not about reading endless no. of books, making notes out of them, and then revising them time and again. Mains is about having optimal subject knowledge (not too less but never too much) of a topic and then utilizing that knowledge to convert a question into a right answer.
In another article, I discussed and demonstrated logically how having just 5 points against various aspects of a topic are sufficient as far as content for mains is concerned. Now we have to learn how to use this 5-points optimal knowledge to write right answers.