Finally

From the time you begin coding, provide comments and documentation for your code. Over the past lifetime, I've coded in very many languages, and will often attempt to write Python code using the syntax of another language.

Ooops!

I will frequently return to my own code examples and cut and paste into new code I'm writing. And if I have kept my code tidy and commented, this passes through into my new code.

As time passes by, new best practices and ways of doing things enter into programming languages. Older techniques are deprecated. When I look at code I wrote in Python 2.x around 2013, none of that code will run now without editing. And some of that code was at the limits of the complexity that Python could support at that time. Refactoring that code so it would run in Python 3.x would be an immense challenge without the level of commenting and documentation that I did.

As for code I wrote in the 1980s……!