I use Paul Graham's advice from his "How You Know" essay http://www.paulgraham.com/know.html

"Reading and experience train your model of the world. And even if you forget the experience or what you read, its effect on your model of the world persists."

Also check out It’s Okay to “Forget” What You Read https://medium.com/the-polymath-project/its-okay-to-forget-w...