Here are my answers to Alkjash's Hammertime Final Exam. I have selected the difficulty level Steel Cudgel of the Lion.
1. Rationality Technique: Ass-in-Gear Mode
This might also be called "buckling-down mode." It's the feeling you get when there is a Yoda Timer running. It's the feeling of being completely focused on the task at hand, and wasting no mental effort on other thoughts. I find this mode easiest to engage when there is a Yoda Timer running, or there is some deadline pressure, but it is possible to engage it when these conditions do not apply, by noticing what it feels like when a Yoda Timer is running and then bringing yourself into that cognitive state at some other time. I'm very productive in this mode, but it's taxing to keep up for long periods. I definitely don't claim credit for this idea, but I claim that the main benefit of Yoda Timers is to make it easier to reach this cognitive state.
3. Cognitive defect, bias, or blind spot: Settled Opinions
I have long felt a strong desire to have settled opinions on things, by which I mean opinions that I have considered carefully, that I can then cache and not have to think about again. I suspect I'm not alone in this (though I'm wary of claiming that it is a universal desire). I think it's close to a truism in this community that impulse should be fought (see the How to Actually Change Your Mind sequence). However, I think there may be a reason why it's actually desirable to have settled opinions (though I don't think this reason yet convinces me that it's a good idea to have settled opinions): having settled opinions allows for temporal coordination between different versions of oneself. If one's views are in constant flux, then it's difficult to plan for the future, since by the time the future arrives, one's values might be radically different. This is analogous to Sunk Cost Faith. So while I currently think it's a good idea to keep one's views open for revision, I think there's a chance that doing so might be knocking down Chesterton's fence, and that it's a good idea to aim for settled beliefs.