How do you keep track of what you've learned?

I know that some people have a giant txt file, some have paper journals, some use note apps

But what about you? How do you keep track of new things you've learned? How has that helped you as an engineer?

Comments

[Ghost]

Good paper, with fountain pen ink of multiple colors on it.

[John Kazer]

Endless onenote pages. Most of which I don't revisit but I think the process of writing helps to remember stuff and sometimes article ideas pop out from the overlap of new and old content

[Mohamed Hassan]

Simple solution => code snippets in TXT files :)