Keep a diary and one day it'll keep you.

The line plays on the double meaning of “keep”: to maintain a diary now, and to be “kept” later—supported, remembered, or even made famous—by what you recorded. It suggests that private, routine documentation can become a form of future security: a storehouse of material for memoir, writing, or self-understanding, and a record that preserves one’s life against forgetfulness. In a show-business context often associated with Mae West, it also hints at publicity and legacy: today’s notes can become tomorrow’s story, shaping how others see you when time has passed.