Does this validate negative self talk that most people say you shouldn't do? Let's say someone (cough me cough) has a lot of weight to lose. I could approach it as either "I've eaten pretty well this week, I can keep doing it" or "Jeez, I'm still a fatty, I need to keep losing weight".
Nearly everyone would say to focus on the first type of statement and not the second, but this article seems to contradict that. I'm sure the amount of magnitude of the negativity would play a role as well.
It sounds like you're focusing on a different dichotomy (positive or negative reinforcement). The two ways of thinking the article deals with are more like (for a diet goal to lose a total of 30 pounds, as an example) "I've already lost 14 pounds" or "I still have 16 pounds to lose". I think the article implies that the former is more likely to lead to congradulatory mindsets, maybe justification for slacking off, while the latter keeps focus on what you have to do to acheive your 'end game'.
As far as focussing on positivity or negativity, most everyone will say think positive, because they want to be encouraging and not seem/feel mean. For yourself though, you need to discover how motivation works for you. There are definitely people who are driven by the things they hate, or at least an emphasis on what needs improvement.
There's a third choice: "I need to do X until Y to reach my goal on time." No negatives, no positives... Simply facts. This is more what the article is suggesting.
However, dieting is a different animal. You aren't building something. You don't have hands-on control of the situation. The best you can do is alter some metadata and hope the right outcome occurs. Less food, more exercise... You can't actually say 'If I jog for 10 more minutes, I'll lose .2 lbs." It just isn't measurable like that.
It is measurable, but it's not as easy as in your example. A single 4-5 hour long run burns a pound of fat (and uses many times that much water) for a moderately fit man. If effort isn't made to regain that fat, it's gone. In general, I think an hour for .2lbs of fat is probably a good bet. Running is one of the greatest fat burning exercises there is, and it also protects muscle and bone density in a way that pure dieting won't. But most people vastly, vastly underestimate the amount of work it takes.
Not sure why this was downvoted, s/he asks a valid question. I didn't read the article, but I know that personally some level of negativity is helpful, because I am very prone to saying "Look, I'm <positive trait/accomplishment>, so I shouldn't worry about not achieving goal X"
Nearly everyone would say to focus on the first type of statement and not the second, but this article seems to contradict that. I'm sure the amount of magnitude of the negativity would play a role as well.