What's your best line?

I thought we might want a place where we can store a collection of good lines to use for different care situations, and for different / difficult / stubborn / narcissistic loved ones. Oh, don't forget we also need comeback lines for those pushy, know-it-all relatives sitting on the sidelines telling us how we should do our jobs.

This is sort of like a bag or a tool box to keep the best and most useful comebacks for various situations. So, that we can come here and look through and choose our tools.

Suggestions: a short set up of a scenario, then a recommended approach to use. Or just list out some good lines you've heard, or read.

A few frequent good lines that I keep seeing:

--Fail to plan is plan to fail
--Failure to plan on your part does not constitute an emergency on my part
--Mom/Dad, what do you plan to do about it? (this puts the ball right back in their court.)

So, what's your best line?