So, people bail on diets. Not just because they're harder than they expected, but because they're so much harder it seems unfair, almost criminally unjust. You can't shake the bitter thought that, "This amount of effort should result in me looking like a panty model."
It applies to everything. America is full of frustrated, broken, baffled people because so many of us think, "If I work this hard, this many hours a week, I should have (a great job, a nice house, a nice car, etc). I don't have that thing, therefore something has corrupted the system and kept me from getting what I deserve, and that something must be (the government, illegal immigrants, my wife, my boss, my bad luck, etc)."
I really think Effort Shock has been one of the major drivers of world events. Think about the whole economic collapse and the bad credit bubble. You can imagine millions of working types saying, "All right, I have NO free time. I work every day, all day. I come home and take care of the kids. We live in a tiny house, with two shitty cars. And we are still deeper in debt every single month." So they borrow and buy on credit because they have this unspoken assumption that, dammit, the universe will surely right itself at some point and the amount of money we should have been making all along (according to our level of effort) will come raining down.
All of it comes back to having those massively skewed expectations of the world. Even the people you think of as pessimists, they got their pessimism by continually seeing the world fail to live up to their expectations, which only happened because their expectations were grossly inaccurate in the first place.
You know that TV show where Gordon Ramsay tours various failing restaurants and swears at the owners until everything is fine again? Every episode is a great example. They all involve some haggard restaurant owner, a half a million dollars in debt, looking exhausted into the camera and saying, "How can we be losing money? I work 90 hours a week!"