You cannot possibly expect to remember everything you learn, whether that be through reading, hearing, or living. It’s impossible to remember it all, even with extensive note-taking, documentation, and systems to help you.
You shouldn’t stress over this fact. Rather, take solace in the fact the most valuable information out there will “stick.” It’ll make a significant impression on you that will last a long time. Perhaps you’ll read entire books only to walk away with one sentence that is of any significance—good. That one sentence is the one that mattered.
This is not to say you should abandon all systems of note-taking or documentation, because those are an essential part of the learning process for now and later. Just don’t stress yourself out by trying to capture any and all information that may become relevant at a later date.