Truth isn't everything.
It's an almost counter-intuitive thing for a skeptic to say, but in some cases truth can be outweighed by the benefit of a lie. The main arguments that I usually see for certain ways of faith-based thinking seem to pivot on the crux of two things:
1) The belief is objectively true: God does exist; vaccines cause autism; the your future is predicted in the stars; a supernatural Chi force runs through meridians in your body.
2) You're objectively better off believing that it's true: A life with religion is more full; believing in Chi flow can help you break concrete with your bare hands.
By the way I have categorized these things, it's clear that I'm operating on the assertion that the things listed above fall under the category of magical thinking. The focus of this post isn't to show the fallacy of believing in the objective truth of these kinds of claims; many people have gone into the minutiae of each issue in much greater detail, and with much more powerful logic than I would. This post is about the second category of argument: that there can - in some cases - be a demonstrable and objective benefit to believing in something that is not objectively true.
The martial art of Kung Fu - among many others - focuses on channeling the flow of a magical force, Chi, to do things would normally be considered to be impossible. Practitioners can often break wood and concrete with their bare hands, rest their weight against a sharpened spear by their throats, and hammer nails into wood with their bodies.
Does that prove that Chi exists? No, of course not. Now we understand the Newtonian concepts of force, acceleration, and kinetic energy. The fact remains, though, that a doctorate in Physics rarely bestows a professor with the ability to smash concrete with his forehead. Chi, it seems, proves to be a useful sort of cognitive shorthand for the massive amount of equivalent mathematical calculations for applying force with your own body. Chi may not exist, but Kung Fu can help you to do things normally considered outside of the range of human capabilities.
You could even test it experimentally. A double-blind study would be effectively impossible, because the experiment's subjects would obviously know whether they were practitioners of a martial art or whether they were the control group. But seeing as how the main purpose of a double-blind experiment is to compensate for placebo effect, I think we could write it off as superfluous; you've either got a broken piece of concrete, or a broken hand - placebo don't enter into it. A simple blinded study, however, would have pretty predictable results: Shaolin Monks can fuck shit up.
In short, Chi isn't real, but it can still help you.
I think there's a valid argument to the idea that truth isn't everything, and that the benefit of believing something that is objectively untrue can make that belief worthwhile. However, it would still be fallacious to conflate proof of a belief's benefit with proof of its veracity.
In this way, kung fu seems to represent an enormous outlier among the many other forms of magical thinking, in that the benefit of its belief can be objectively measured. Nobody would argue with the fact that if your goal is to break a brick with your body, you're better off knowing kung fu than not knowing it.
How do other forms of magical thinking such as religion, homeopathy, and astrology compare against kung fu? Not well. "Natural Medicine" and Astrology can and have been easily subjected to controlled study, and both have failed, with flying colours, to show any efficacy beyond the Placebo/Barnum effect and random chance. Astrology is nothing more than vague cold-reads guessing at random chance. No atheists that I know lead any less happy a life for their lack of superstitious belief in a god. Controlling for medical history and lifestyle, you're statistically about as well off going to a homeopath as you are doing nothing, and substantially less well off than going to see a real doctor who knows what he or she is talking about.
The funny thing about homeopathy is that the reverse used to be true. Before the advent of germ theory, vaccination, and basic procedures of hygiene and sanitation, mainstream medicine once did more harm than good. Common now-debunked treatments for various physical and mental illnesses once included bloodletting, lobotomy, electroshock (which has been discontinued in all but a select few rare cases where it can actually potentially help), and avoidance of bathing. If you lived in the 18th century, you'd often be better off having a homeopath playing magician and effectively doing nothing than you would going to a doctor and being bled by unsanitized equipment.
Eventually, though, the mainstream of medicine came to test treatments ojectively. Those treatments that did not prove to be effective were discarded, and those that worked were incorporated into the canon of modern medicine. Homeopathy is still making things up and doing nothing, and so has been surpassed by modern medicine as the treatment of choice for any reasonable person who wants to deal with something like AIDS, cancer, or internal bleeding.
It's 5:45am right now, so I'll get to my point.
I'm not a practitioner of kung fu, but if I wanted to break things in cool and objectively measurable ways, I'd be better off it I were.
I'm not a denizen of the 18th century, but if I were, I'd be better off going to a quack doctor selling me water and snake oil that did nothing than I would going to a doctor who wanted to open up my blood vessels with a dirty needle.
It's mostly a rhetorical point, but a belief doesn't need to be true for it to be a worthwhile one; it needs to be either true or demonstrably beneficial. I feel extremely confident in saying that in the modern world, most forms of magical thinking (god, zodiac signs, homeopathy, &c.) fail in both regards. Kung Fu (believing in Chi flow) and homeopathic medicine (when - and only when - compared to the mainstream medicine of a couple centuries ago) are not the rule, but the exceptions.