|Sooner or later you will eat a chocolate cake.|
You have fallen off the wagon, your diet and, by extension, your life is over. There is nothing more to look forward to now but public humiliation, pretending to be jolly and type II diabetes.
The first thing to remember is that, if you want to lose weight and keep it off, dieting is, like malaria and a lingering sense of injustice, for life. This is the longest of long term projects and the occasional 'lapse' is not only not important it isn't actually going to matter at all. I allow myself an indulgence once or twice a week and thus far I've stuck to the 1kg a week loss that I planned for(1).
The occasional midnight tryst with a chocolate cake is not what is going to break your diet the things that are going to break your diet are: a) creeping calorie count and b) lying to yourself.
As the first exciting bloom of your diet wears off and you find that despite your hard won loss of many kilograms your social life has failed to improve, staff in clothes shops still give you the look(2) and you still cringe when you see pictures of yourself, you'll find yourself cheating. Just a little bit something extra there, a wafer thin chocolate mint. full fat milk... what is not important it is the accumulative increase in daily calories that counts.
This is where your food diary helps, check your totals, make sure that 13 times out of 14 (or so) you stay under your calorie limit. The same applies to your weekly weigh-in, if you cease to lose weight or put it on for more two weeks running you are not retaining water or wearing heavy socks you are eating too much. From this you can see why lying to yourself is so damaging - if you can't monitor yourself you can't stop the calorie creep and you're fucked.
So say yes to the occasional binge but no to calorie creep and you too might go from having your own gravitational field to merely being designated bad guy in a Harry Potter film.
(1) That's right in a mere 52 weeks I will be merely morbidly obese.
(2) You know the look I'm talking about and if you don't then you've never gone clothes shopping while fat. That's right - that look.