Once there was a truck driver maneuvering his gigantic semi on narrow street. I thought I'd be helpful and offer suggestions. He interrupted me and told me to bugger off.

Ok, I backed off and then watched.

The guy moved that truck around like a ballerina. It was a pleasure watching him handle it, a true pro.

The lesson for me was to not tell someone you just met how to do their job. It's a lesson I've had to learn many times.