Edited for concreteness.
Exactly one year ago, LessWrong helped me change my mind about something important.
Since then, my life has been changing very rapidly, as a direct result of the rationalist community. I got in touch with other rationalists in person, which made my social life vastly more interesting (not to say surreal). My plans for the future have definitely shifted a bit. I began a deliberate habit of trying new things and learning new skills, and facing up to my flaws, often with advice from LessWrongers or IRL rationalist friends.
A few examples: I improved my diet (paleo), tried yoga, took up cognitive behavioral therapy to work on some chronic insecurities, moved Python from the "wish I knew" box to the "have a detailed plan to learn" box, dared to publish some popular-science articles under my real name, learned to do Fermi calculations in my head. I also noticed that my habits of thought have been changing: for one thing, I'm getting better calibrated about probabilities -- I'm better at estimating how I did on schoolwork. For another thing, I'm getting better at not reflexively dismissing non-standard ideas: the first time someone mentioned me that a good statistician could make a lot of money in car insurance by finding new correlations to monetize, I thought "Car insurance? Hmph, low status." The second time I heard that suggestion, about five months later, I thought "Hey, that's a decent idea." Some of these changes have begun to show results -- the time-management habits* I came up with have started to improve my academic performance, and I notice I'm far less inhibited about taking the initiative to work on projects (I have a couple of interesting balls in the air now, including a business idea and some volunteer work for SIAI, whereas I used to be very reluctant to volunteer for things.) I've become much more open to cold-emailing people who work on interesting things (on one occasion I got a job offer out of an AI researcher); I'm more comfortable viewing myself as a junior member of the Interesting-People Club. I made a unilateral decision to be happier, and though I hate to jinx it, I think it's working.
I say this just to offer evidence that something about "rationality" works. I'm not sure what it is; many of the components of LessWrong-style rationality exist elsewhere (cognitive biases are fairly common knowledge; self-improvement hacks aren't unique to LessWrong; Bayesian statistics wasn't news to me when I got here). If anything, it's the sense that rationality can be an art, a superpower, a movement. It's the very fact of consolidating and giving a name and culture to the ideas surrounding how humans can think clearly. I'm never sure how much of that is a subjective primate in-group thing, but I'm hesitant to be too suspicious -- I don't want to blow out the spark before the fire has even started. My point is, there's something here that's worthwhile. It's not just social hour for nerds (not that we can't enjoy that aspect) -- it actually is possible to reach out to people and make a difference in how they live and see the world.
Once upon a time -- it seems like ages ago -- I used to envy a certain kind of person. The kind who has confidence that he can make a decent stab at ethical behavior without the threat of divine wrath. The kind who thinks that human beings have something to be proud of, that we're getting better at understanding the world and fitfully reducing suffering and injustice. The kind who thinks that he, personally, has some chance to make a valuable contribution. The kind who's audacious, who won't let anybody tell him what to think. The kind who whistles as he wins. Bertrand Russell seemed to be like that; also Robert Heinlein, and a couple of close friends of mine. That attitude, to me, seemed like a world of cloudless blue sky -- what a pity that I couldn't go there!
Ah, folly. Thing is, none of that attitude, strictly speaking, is rationality -- it might be what comes before rationality. It might be what makes rationality seem worthwhile. It might simply be the way you think if you read a lot of science fiction in your youth. But I've never seen it encouraged so well as here. When people ask me "What's a rationalist anyway," I tell them it's living the empirical life: trying to look at everything as though it's science, not just the lab -- trying different things and seeing what works, trying to actually learn from everything you observe.
I'm grateful for all this. While it's probably for the best that we don't pat ourselves on the back too much, I'm convinced that we should notice and appreciate what works. I used to be uncomfortable with evangelism, but now I tend to refer people to LessWrong when they mention a related idea (like complaining about incoherent arguments in debates). I think more visibility for us would be a good thing. I have plans to make a "rationality toy" of sorts -- I know other people have projects in that vein -- the more things we can create beyond the blog, the more alternate channels people have to learn about these ideas. And the more we can inspire the less confident among us that yes, you can do something, you can contribute.
*My anti-procrastination tactics are goal tracking via Joe's Goals and selective internet blocking via Self Control. Also posting my weekly goals to the New York Less Wrong mailing list. My problem up until now has really been spending too few hours on work -- in the bad old days I would frequently spend only 5 hours working on a weekday or 3 hours on a Saturday and the rest fooling around on the internet. I was really hooked on the intermittent stimulation of certain message boards, which I'm mostly glad to have given up. Now I'm aiming for 60-hour weeks. One thing that works in my favor is that I've almost completely stopped motivating myself by the ideal of being a "good girl" who receives approval; the reason I'm trying to get more work done is so that I can get credentials and preparation for the life I actually want to lead. I'm trying to be strategic, not ascetic. I don't know if what I've done is enough -- there's always someone who works harder or longer and seems to never need a break. But it's definitely better than nothing.