The notebook I keep next to the keyboard

Every few months I try to replace the paper notebook beside my keyboard with an app. It never sticks.

The reason is speed. When I'm debugging, the thought I want to keep lasts about four seconds. Opening a note app costs more than that. A notebook costs one.

What helps is writing down the smallest useful thing: the command that failed, the value I expected, the value I got. Later, when the same failure comes back, that line is faster than any search.

If you want the history of the thing, the notebook article on Wikipedia is a decent read.