The old joke goes like this:

Crew desk: Captain, I know you're on days off but we have a trip for you.
Gezer Capt: No can do. I've been drinking.
Crew desk: Oh, that's OK. The trip is for tomorrow morning.
Gezer Capt: Still no can do.
Crew desk: Why is that?
Gezer Capt: I'm drinking and I can't stop!

Never answer your phone on your day off and/or get distinctive ring or (caller ID)