I've linked the important Gollwitzer paper before, the one on Goal Shielding and Implementation Intentions.
One particular phrase from it was game-changing for me. It introduced a concept called "The Elaborated Intrusive Theory of Desire."
Here you go. It's technical, but worth it --
The elaborated intrusion theory of desire (EITD; Kavanagh et al., 2005) proposes that the intrusive effects of desire result from the interplay of automatic and deliberative processes. External cues trigger spontaneous thoughts about the target that are perceived as intrusive. These intrusive thoughts are the result of learned cue–target associations and place little demand on cognitive resources. However, when the intrusive thoughts elicit a strong affective reaction or provoke the experience of deprivation, then the thought will become elaborated, which requires controlled processes. Progressive elaboration of the target-related thoughts is the mechanism that explains the persistence and influence of desire. Elaboration alters the prioritization of attentional and working memory processes, making it likely that additional internal/external cues are accessed and that further intrusive thoughts are generated. The processing priority that is accorded to elaborating thoughts about the target explains why progress toward superordinate goals (e.g., the dieting goal) often is undermined during craving episodes.
In short -- a simple craving happens spontaneously... but then if it's perceived as harmful and sets off an internal battle of sorts in a person, the craving and desire get "elaborated" and start... hijacking your mind? "Hijacking your mind" is probably too strong a way of putting it; but not altogether crazily too strong.
Basically, the more you start doing "I want that... I shouldn't want that! But I do, I want it! No, I shouldn't! No! ... but I want it!..." -- when you do that, the mind seems to prioritize the issue as more important, and it starts choking off your mental resources to go to other tasks; a vicious spiral ensues; etc.
Just knowing the term EITD helped me get a mental reference point that helps my a life a lot. I can say to myself, "Oh, stop EITD'ing myself here" -- and it actually works some of the time.
Again, I recommend reading the paper. And stop doing the EITD thing to yourself.