This is a quote attributed to a number of different people, earliest by Hunter S. Thompson, Bill McKenna and a Maxine cartoon. Likely more.

Here is a link that might be useful: Here are some examples.

Don, like you, I searched for the author, but I could not find a definite answer. In some examples the drink changed, such as to a martini, wine etc... but the chocolate held steady. Works for me.

All I have to say is, that is one motto that I am living! Too deeply. Better quit before the grave finds me sooner rather than later.