It seems to me a general truth that people who focus so much on "personal responsibility" and "willpower" are people who are much less interested in solving problems, and much more interested in making themselves feel superior by way of their own good fortune. The line your advocating is equivalent to "Just say no to drugs" or abstinence-only sex education.
Then this will probably be a real mindfuck then:
I'm a rather hardcore liberal, and I believe that the focus should in fact be on "personal responsibility" and "willpower".
Further, we should work on teaching not only how to apply those concepts, but the best ways to do so as part of public health education and (in schools) home ec. and PE (you know, those things that we've slowly worked on purging in favor of bland, guaranteed-not-to-anger-parents "replacements".)
Yes, you can't teach "willpower", but you can teach personal responsibility, and you can give people the tools to help better themselves and support throughout the process. And as a liberal, that's exactly what I think we should do.
I'm glad you mentioned sex and drugs. Because you know what is most effective at preventing pregnancy? Not fucking. And that's one of the things that we can teach in sex ed. But because I'm not a far-right idiot, I *also* believe in providing additional lines of defense (condom distribution, better public health support, Planned Parenthood clinics, etc.)
It's the same thing with food. You know what's most effective? Eating less. And yeah, like not fucking it can be pretty hard when the temptation's staring you in the face. And some people will fail at that, which is why in addition to trying to teach restraint we should also provide additional lines of defense (reduce corn subsidies, continue improving food science, require truth in advertising for fast food, fix school lunches, etc.)