Sigmund Freud, who got so many things wrong that it's hard to accept that there is even a remote possibility that he got anything right, may have had something in his theories about "fixation". In particular, I'm thinking about "oral fixation" which some believe may be related to over-eating. Oh, I don't believe for a second those who are arrested at a childhood developmental stage that makes them orally fixated may go on to focus on oral sex, but it does seem that a lot of people with weight problems are stuck on the idea that they are still children in some ways.
Recently, I've been reading lots of discussions by people trying to lose weight in which they feel it is essential that they rough themselves up a bit when they screw up on their "diets". People who forgive themselves and move on are seen as being at risk of not staying the course. The underlying idea is that if you don't beat yourself up (or even better yet for the smug forum members, allow others to beat you up) as a form of "punishment", you won't take your lapse seriously and are going to eat too much again because you'll see being off your plan as "no big deal".
This is a sort of thinking that I haven't subscribed to, and still do not for a variety of reasons. The main reason is that most of the folks who are trying to lose weight are not pre-verbal toddlers who only understand the equivalent of "bad girl!" The idea that we, as adults, require overt "punishment" to keep us on track with our food plans is one of those simplistic notions that does not sit well with me. Are we dogs to be hit with a rolled up newspaper when we have an accident? Are we children whose hands need to be slapped away from the cookie jar? We are not, and treating ourselves in this manner is not only misplaced, but destructive to weight loss efforts.
Imagine that you have a child who is trying to learn to ride a bicycle without training wheels. When he falls off, you don't say, "You are a clumsy child! Get back on and try again." If every time he falls off, you say, "You have to stop doing that! You're never going to succeed if you don't stop falling off!", what is the likely consequence? The likely result is that the child will give up. The focus will be on the lack of success and the negative traits which lead to failure.
We understand the consequences of our actions on a logical level, and abusing ourselves on an emotional level is only going to be counterproductive. Telling yourself that you have to have more "willpower" or that you are "weak" and need to be "strong", or worse, that you are a bad person who is lazy and out of control will only create a mantra that will make you feel less capable of realizing your potential. After some time, the negative words used to berate oneself are internalized and increase the chances of failure, not success. You become weaker, not stronger, when approaching life changes. This applies to everything, not only weight loss.
This is the same reason why abusing fat people for being fat doesn't motivate them to lose weight. Abuse from any source only makes it harder to succeed. It has no positive value in instigating desired long-term changes. None.
The best course of action for falling off the horse isn't to castigate yourself for the fall and then get back on. The best course is to thoughtfully consider what caused you to fall off and how you can avoid doing so next time and then to get back on with a renewed sense of confidence due to your having a new course of action at your disposal. We are not children who need to have fingers wagged at us, bottoms metaphorically swatted, or to be told that we've been naughty, and treating ourselves as such is counterproductive.