Ask HN: How do you build up the knowledge base over time?

What does it take for one to capture these kind of detail eg. mathematical background, debugging session, some new concepts, some old concepts, system design etc? With age, I feel like my memory can't sustain the amount of information I am accumulating. Therefore, I think I will need to build a quick reference or memorize things as I go.

Normally, I do not like note keeping because my notes are never authentic to the original source. Thus, they are rarely useful. I have a bad habit of going through the same source multiple times. It is highly effective but unsustainable because of the time constraint. It was well suited for college when I had time.

What are other alternatives for this issue? I would really like to get some insights from those who have gone through these issue or face the issue.

Thank you for your time!

Cheers.

PS: As we build a software, we get lot of artifacts as byproduct. I also want the snippets or highlights to be a byproduct of my work such that I will be motivated to build a proper documentation out it!