Good advice reflects the nature of the endeavor, and therefore its effect will be in proportion to how well the advice was followed, which is how well the actions correspond to the ideal. Bad advice is always something which is trying to fight nature, and force it into the desired pattern, instead of working with it. Less than 100% effort with such advice has no chance of forcing nature out of its routine; even a 100% effort has no guarantee of positive results.
One public example is the debate over improving the economy. Obama and his economic advisors know how to fix the economy, but their programs will only work if they are implemented fully. If the Republicans limit the size of the stimulus and other economic programs, they have gutted them, leaving them with no chance of success. If the stimulus failed to stimulate the economy, that is only because it was not big enough, and 99% of the necessary stimulus is insufficient.
If economies in crises can be revived with stimulus spending, then a small stimulus would have a small, but noticable, effect. The argument that it was not big enough does not explain why it failed completely, and rather demonstrates that it failed because stimulus spending is not a valid economic approach.
Arguing for 100% effort means that advice is not testable. You can never know if what you are doing is right until you have invested everything in it, and even then there is no way you have reached the necessary level of investment. Advice which will only work with 100% effort is not worth following, because you have no reason to ever expect the advice to work.
Bad advice will always make the Red Queen’s claim: running as fast as you can is will only let you stay where you are, and you must run faster than that if you are to get anywhere.
Another area where such advice is common is standard marriage advice. Many counselors who offer platitudes on marriage will tell people that marriage is very hard work, and unless they invest 100% it will never work. Standard marriage advice is pretty clueless, and will not offer much when there are real problems. The counselor’s exhortions that marriage needs a 100% investment make his advice untestable and unfalsifiable, but they do not make it useful. Good marriage advice will improve the marriage even when partially applied.
Good advice will never reach 100% compliance. Bad advice needs 100%, because until then there is no return on the investment. Good advice will have a noticable effect even when partially applied, and the benefits of the advice will increase with the effort. Good advice followed with 90% consistency will give people what they are looking for, and usually it will give them far more than they expected. The additional effort will have lower returns, as the effort needed gets more difficult, and anyway the desired results have already been achieved. When someone has followed good advice the extra effort needed to go 100% cannot be justified. At that point they have little to gain from that extra effort.
Bad advice is worthless with less than 100% effort, and any advisor saying that his advice demands 100% is exposing the worthlessness of his advice. When advice is on target, 100% is not only not necessary, it is also irrelevant. Good advice can be sampled, tested, and adapted, and will always show results.