The different reactions to the text book certainly do point to the different needs of the students you're teaching--they may have more dissimilarities than similarities. Your approach of trying to get them to cultivate the mind-set and habits that will make for success sounds like a good one (though man, my years of editing business English makes me extra sensitive to phrases like "peak performer"--they just grate on my nerves--and yet I know that it's easier to just pick some epithet like that and use it than it is to keep on saying some long string of words about work habits, etc.

What you say about the lifestyles also strikes me as a hard thing... the fact that the students aren't necessarily living this way out of choice but out of necessity... I remember when we were living on a really limited budget--it would have been nice to buy organic foods and whole grain bread and so on, but the cost! So we went for the less nutritious alternatives, which could at least feed all of us. Similarly with knowing that it's good to get a full night's sleep, and yet you want to earn enough to pay the bills and go to school--etc. etc. Such an impossible bind, sometimes.