The quote applies to much of life, and it most certainly applies to self-education. If you wholeheartedly embrace the industrial model, including the industrial model of education that our current formal system of education is based upon, you will not fully embrace you and your uniqueness. Your education, like everything you pursue, must be undertaken to maximize your individuality, not minimize it as the industrial model will continually try to do.
Here’s the quote from Mamet. I hope you find it inspiring.
Do not internalize the industrial model. You are not one of the myriad of interchangeable pieces, but a unique human being, and if you’ve got something to say, say it, and think well of yourself while you’re learning to say it better.