Why? What purpose do you have for textbook physics? Think of what you're going to do with that knowledge. Are you going to become a physics teacher? Do you just want to impress "a bunch of folks on the internet"?
The time in your life for grinding on textbook knowledge is over. That was age 0 to {insert age at end of college/academic career} non-inclusive.
Think very carefully where you want to spend your motivation and discipline.
Understanding the "Why" important. However, it seems clear that he/she has already answered that question, and now they are trying to figure out the "how". Knowledge is power no matter where it comes from - a textbook, the internet, a master or simply studying the natural world. Seems odd to discourage someone from expanding their understanding of the world.
The time in your life for grinding on textbook knowledge is over. That was age 0 to {insert age at end of college/academic career} non-inclusive.
Think very carefully where you want to spend your motivation and discipline.