Well, the motte is "I'm very epistemically humble", and the bailey is "that's why I'm always right".
No, not really? I generally ignore anything Scott writes which could be described as 'agreeing with Yud' -- it's his other work I find valuable, work I wouldn't expect Yud to write in any style.
I think there's a tendency to assume the rationalist community has all the answers (e.g. The Correct Contrarian Cluster), which seems (a) wrong to me on the object-level, but also (b) at odds with a lot of other rationalist ideas.
If you point this out, you might hear someone say they're "only an aspiring rationalist", or "that's in the sequences", or "rationalists already believe that". Which can seem like a Motte and Bailey, if it doesn't actually dent their self-confidence at all.
I'd like to know that too! I've had some fairly moving meditative experiences, but still find it oddly aversive to do; strength training feels easier, just because my reward system seems to understand it better.
I think joining a meditation class can help, as you get a social context and a schedule, but that does depend on having a good teacher nearby.
Maybe strength training? It made a big difference for me, and I wouldn't have expected that going in.
The key is to do it regularly, even if you don't do a lot; ten minutes every other day is fine, and you can do it at home with bodyweight or resistance cables.
(Meditation is also great, but I assume most LWers will have thought of that.)