All-or-Nothing Thinking
All-or-nothing thinking grades performance as either complete success or total failure, with nothing in between. The exercise literature's working definition is sharper than the general one and this publication has adopted it: a person who cannot adhere perfectly to their plan chooses not to exercise at all rather than modify the plan. The broad cognitive pattern is long established in clinical psychology. The exercise-specific research is under a year old, describes itself as examining an overlooked barrier, and is therefore live ground rather than settled ground.
What it is
A plan of five sessions a week survives eleven days. A work trip takes out Tuesday. The reasonable move is four sessions that week, or twenty minutes instead of an hour. What happens instead is that the week is written off, and then the plan is, because the plan was the kind of thing you either do properly or do not do at all.
That is the whole mechanism. The distortion is not in wanting to train. It is in the grading scheme, which has two boxes and no partial credit, so a modified session scores the same as no session and there is no reason to bother with it.
How this differs from the abstinence violation effect, and why both pages exist. The abstinence violation effect is the specific relapse mechanism named by Marlatt and Gordon in 1985: the cognitive and emotional reaction to a lapse, in particular attributing the slip to personal failure rather than to circumstance, which raises the odds of a full relapse. All-or-nothing thinking is the broader cognitive pattern that makes such an attribution likely in the first place, and it is already present in how the plan was framed, before any lapse has happened. One is a thinking style, the other is what happens after a breach. Neither should be folded into the other.