What is the meaning of [Failing to plan is planning to fail]

Literal meaning .

This modern-day proverb is widely attributed to Alan Lakein, the writer of several self-help books on time management from the 1970s onward. The quotation is certainly in the gung-ho, up and at ’em style of Lakein’s and he may well have coined it. I can’t find the source of the quotation in his published work, so ‘attributed to’ is the best I can do for now.

If Lakein did coin the expression, he must have done it before 1979, when it appeared in print in an article by Ron Watmough, in the Small Business section of the Canadian newspaper The Lethbridge Herald, May 1979.