You've spent a few years eating poorly: lots of junk food, very little in the way of unprocessed, healthy foods. Perhaps this is the way you learned to eat as a child and you never knew there was any other way to do things, so you've developed a lifelong habit of overeating "garbage".
To makes things worse, ever since you were old enough to get your license, "moving you body" has meant getting in the car to get from point A to point B. Your idea of exercise was taking out the garbage or looking for the TV remote control.
And then, one day (or over a period of time), you realized that something was wrong with the picture. Maybe it was constant acid reflux, high blood pressure or just simply not liking what you saw in the mirror.
And you resolved to make a change...a RADICAL change: no more junk food, lots more fresh food; no more driving when you could easily walk; maybe the decision to buy a bike for exercise, or join a gym.
And you really went for it, heart and soul. You made the changes; you felt better, lighter, pleased as punch with yourself.
Suddenly, life threw you a curve ball (or two or 27) and all these recent good habits seemed just too hard to keep up. And you went back to the bad old days.
Here's what I'm wondering. And here's where the heresy comes in.
Is there middle ground between the "bad old days" and perfection in all that you eat and do all the time?
If you can't take the heat (i.e. always being on plan), is the only alternative to get out of the fire (and binge to your heart's content)?
Do you have to chose between the way of the warrior or the way of the slug?
Is it all or nothing?
Is it the fast lane or the no lane?
Or can you find a "middle way"--slow, with fits and starts, but your way and your speed?
Even if you drop off the diet bandwagon for awhile, does it mean that your only alternative is to go back to the bad habits? Can't you keeping applying those new, better eating habits, even if you're not formally on a diet? Can't you keep up that evening walk, even if you let your gym membership slip?...
And in so doing, keep building the new habits until, slowly, they become second nature?