In my own case, I had been taught the golden rule of "use the style that is already in use" - which I admit, was a hard lesson when I was young I admit.

In my first Unix job (roughly 40 years ago), I read the vi reference manual and memorized the keystroke commands.  And then did
   % cd /user/include
   % vi *.h
to fix up all the indents and comments.

Later on I graduated to learning not to do control-p on a Vax console a second time.

What were your mistakes?  ("Always mount a scratch monkey")