Makes me think the folks who are uttering it are on the wrong wagon.
If your goal is simply to do your best, there's really never any need to fall off any moving objects.
Sure, you might for various reasons make nutritionally or calorically frightening choices, but so long as you asked yourself those two ever important questions, "Is it worth it", and, "How much do I need to be happily satisfied", there can't be a wrong choice.
Sometimes your best may be a basket of chicken wings but perhaps a smaller basket than normal and one less beer, or a fancy coffee with whip just ordered less frequently, or Chinese take out minus the calorie-insane General Tsao's staple, or a bowl of ice-cream instead of a pint, or a small bag of chips rather than the giant bag, or a full-sized chocolate bar rather than a Blizzard.
What I'm getting at is that sometimes we make choices that are less than ideal, but that so long as you've made your best worst choice, you're still doing great!