I think you're basically right, although there's also a large and important signaling component: it's in fact good to signal willingness to complete projects if you want people to work on projects with you.

Also, as I understand it, this was exactly C. S. Lewis' attitude towards faith. I don't have a convenient pull quote though.

I'm curious what are the "ejector seats" that you mention in this post and in Day 1 post, that can help with the time sinks and planning. While other concepts seem familiar, I don't think I heared about the ejector seats before. I can guess that those are something like TAP's with the action of "adandoning current project/activity". Looking forward to your Day 10 post on planning that will hopefully have an in depth explanation and best practices of building those.

Thanks for the sequence that focuses on instrumental every-day rationality.

I like the analogy you give for why sometimes "toughing it out" can be viable, especially if your estimates are going to be changing over time.

One specific area where I'm sure that the sunk cost fallacy is actually Just Bad, though, is in finance / gambling related matters. It causes people to consistently underperform vs if they had just stuck to some heuristics or something.

Epistemic status: I was told to argue this position. 

For a long-term project (say, for example, finishing a PHD rather than mastering out), the true utility you'll derive from it is a random variable with some true mean and variance. Maybe finishing the PHD will take 8 years and you'll never get that TT position you dream of, maybe it'll take 5 and there will be a perfect job for you at the end. You can't know the true mean utility, your guess of the mean is an estimator, which is itself a random variable. I think your argument was that sometimes your estimate of the mean utility will be negative, but that the true mean utility will be positive. So you should stick through and see if it improves. But the inverse can also be true - you can have cases where your estimate of the mean is positive and the true mean is negative. So "stick with things even though your estimate of the mean utility you'll derive from it is negative because it might actually be positive in reality" seems like as logical a rule as "drop things even though your estimate of the mean utility is positive because it might actually be negative."

I think you're right and I appreciate this post a lot. You described a lot of experiences I've had but your random walk example is something I'll remember for a long time. Just as I should do more favors for my future self, I should have more faith in my past self. 

"Finishing things" is a skill I would love to get better it. It's difficult because most of my internal motivation for projects come from the first 60% - 90% of it, but almost all of the social or external rewards come from finishing the thing (and the long tail of chores in the last 1% - 5%). So I end up doing a lot of "internally impressive" things, but having nothing to show for it (unreleased compositions, unused skills/knowledge, etc).

There are many benefits I'm missing out on from not having faith in past me and pushing through the last few steps. Thank you for making me think about that.

It seems to me like the "random walk" case you described is poorly formed; the possibility of a project turning out to be worth it after all should be factored into one's estimate of how "worth it" it is. If it doesn't, then that's a problem of motivated reasoning, not a reason to have a sunk cost fallacy.

Intentionally inducing fallacious reasoning in oneself is classified as "Dark Arts" for a reason, especially since it can bias one's own assessment of how well it turns out and whether to continue doing it.

I'd probably put it this way – the Sunk Cost Fallacy is Mostly Bad, but motivated reasoning may lead to frequent false positive detections of it when it's not actually relevant. There are two broad categories where sunk cost considerations come into play, a) cases where aborting a project feels really aversive because so much has gone into it already, and b) cases where on some level you really want to abort a project, e.g. because the fun part is over or your motivation has decreased over time. In type a cases, knowing about the fallacy is really useful. In type b cases, knowing about the fallacy is potentially harmful because it's yet another instrument to rationalize quitting an actually worthwhile project.

You can use a hammer to drive nails into walls, or you can use a hammer to hurt people. The sunk cost fallacy may be a "tool" with higher than usual risk of hurting yourself. This is probably a very blurry/grayscale distinction that varies a lot between individuals however, and not a clear cut one about this particular tool being bad. But I definitely agree it makes a lot of sense to talk about the drawbacks of that particular concept as there is an unusually clear failure mode involved (as described in the post).

The "Focusing for Skeptics" post doesn't seem to exist at the link you gave anymore. Do you know where I can find it?