I know exactly how you feel! I'd have weeks of good eating and then bam, one evening I'd have one too many of a healthy snack, which leads to an unhealthy snack and everything starts to snowball downwards from there. I have no explanation for you as I'm trying to work through it myself. Afterwards, I'd sit down and write about how I felt the entire day and leading up to the binge and then afterwards. I'd isolated that I tend to binge in the afternoon/evening and on particularly cold/rainy days when I'm home alone. I guess in the past I had associated this environment with sadness so now even when there's nothing to be sad about, I'd subconsciously start eating more. And then I'd come up with ideas/plans to handle it when I feel the urge to overeat coming on. I monitor the weather like a hawk and prepare for my "rainy day blues".
You're a lot smarter than I was because you know to forgive yourself. It took me months of being disappointed in myself (which lead to a falling off the wagon) until I finally realized that beating myself up over these binges was just making it worse.
From the last time I was successful in losing this weight, as the weight came off, I didn't binge as often and even then my "binges" got less and less extreme. Eventually my body learned to not desire bad foods or foods in huge quantity. Of course there were occasional slip ups, but you know what, I realized that even skinny people have days when they eat a little too much. It's not *that* crazy and sometimes you have to let yourself go a little (some even say the little burst of energy is good in "shocking" up your metabolism). One day of eating a little too much isn't going to derail months of effort. We just have to make a conscious effort to not let the one day/afternoon become a habit.
I completely feel you on the frustration, but what can you do? We're only human. Gotta accept us in all of our great flaws.

Good luck!