I was working on some tight deadlines while at a cafe.
Overwhelmingly, I had the urge to break from my diet and order a bunch of junk food - sandwiches, french fries, etc.
I'm not exactly sure why that urge comes up, but I think it's quite common. You've probably experienced it, yes?
If you're trying to refine your diet, or stop binge drinking, or sleep at a reasonable hour, or quit some bad habit, or... whatever... well, how have you gotten off track in the past?
Probably when there was a "good reason" - either something more important (like a deadline) or some general exception (like a "special occasion").
This has happened to me, too. But I've found the phrase in the title, comical as it sounds, helps a person stay grounded. "Self destruction is generally counterproductive."
Here's how it works in thinking:
Impulsive thought: I should have some cake, french fries, and drink two bottles of brandy. Just right now, the deadlines [or "special occasion"] are more important than the overarching plans I've set.
Conscious thought: Wait, self destruction is generally counterproductive. I set up the rules for my life because my life will go better if I follow them. Even if there's a short term gain here - there might not be, even - it's the kind of tradeoff that doesn't make sense and works against you. I'll order a salad.
Also, on days where I'm close to breaking a hard rule, I'll absolutely sacrifice a soft objective to refrain. The end goal of how I eat is high energy levels, good general-health, good longevity, and a very lean physique. Eating a gigantic pack of peanuts would be contrary to the objective, but I'll go for it on a particularly tough day in order too not break the hard rules. Hard rules become easier to break the more often they're broken, whereas sacrificing a softer objective doesn't seem to trigger the same downward spiral chain reaction.