Advice from Nelson Algren

Never play cards with a man called Doc.
Never eat at a place called Mom's.
Never sleep with a woman whose troubles are worse than your own.

This is from A Walk on the Wild Side, of course.
I probably shouldn't even quote it here since it is so famous, but, well, I heard it on the radio today, and after I switched the gender in the last sentence, it made a Hell of a lot of sense.