In one case the self-depreciation is only postponing a much needed lifestyle adjustment, while the other its a way of dealing with a problem that just can't be fixed with a diet and exercise. Constructive criticism is one form of good feedback, the other is blunt opinion. But while both are important, most of us will deeply resent the latter unless it's positive. If sugar coated feedback becomes a substitute for real work satisfaction then you become a feedback junkie who can't quit. By Grabthar's hammer, what a burn.
Feedback needs to be nasty and sting when it has to.
There is no point in going for the perhiphery, make a stab at the beating heart. If you're steeped in the kind of dialog that passes for feedback on web site forums, then you'll understand the difference between those who swat inconsequential flies and those who's fangs have sunk into a jugular. The days have passed when we needed lots of verbal encouragement from our parents to learn how to walk, ride a bike or read. We're not babies anymore and the encouragement must now come from seeing genuine satisfaction with our work. Genuine and sincere feedback comes in the form of more tips in the jar, an increasing audience, and lots of repeat business.