Speaking for myself, on the rare occasions in my life when I've taken a psychedelic (LSD or psilocybin, never DMT as here), I've found the experience useful simply because such a radical change of perspective offers access to insight which might not be available in a more ordinary frame of mind. Such insight is, in my experience, occasionally of value. Of course, such insight is, also in my experience, much more often the kind of thing that makes sense only in hindsight and with the benefit of confirmation bias, which is to say, it doesn't make sense at all.

I think it's very easy for people to make too much of experiences like these; to be taken out of the world, as these substances do, can be wonderful or terrible or both at once, but I can't imagine a case in which it could be neither, and our culture doesn't really provide a good conceptual framework for dealing with wonder and terror. And I know with certainty that it's very easy to talk such an experience to death; in the case where it does offer beneficial insight, such insight is generally of such an intimately personal nature, and so inextricably bound up in one's unique and individual experience of reality, that to try to make it comprehensible to others is often to make it incomprehensible to oneself. At the very least, you want to let it settle a good long while, and integrate into your personality if it's going to do so, before you try to elucidate it to someone else - and, beyond that, there's a very solid point to be made that, if it really is going to change you, it'll do so in a way that doesn't need to be explained to anyone.

Whether any of what I've just described has any use to you, I have no idea, and this is the kind of question you could ask five people and get twelve answers in any case. But maybe it's been worth your while; in any case, I hope it has. I'm happy to answer any further questions it might elicit, although of course I can't promise those answers will be any more useful than this one has been.

The emotional effect of the easing of an almost entirely unconsidered but omnipresent background note of minor but real and adamantine anxiety is completely personal, but I would by analogy describe the before-and-after as if a decades-old background musical harmonic dissonance were suddenly reframed by the addition of a new bass note, which integrated them into a satisfying (and hitherto unimagined) chord.

I could describe the specifics, but I'm trying to avoid the cliché of sharing dream content with the expectation that its logic and e.g. discernible ties to everyday consciousness can somehow be translated and made of interest...

...I fear those are just deep-sea fish that are better discussed at a remove, or, alluded to rather than named.

If that makes any more sense itself. :)

Maybe a more direct TL;DR would be, _a long-standing semi-conscious fear which had resurfaced repeatedly in disturbing dream, was revisited and unexpectedly resolved in such a way that I came away with greater serenity, which has persisted now for many years after the experience_.

That might be akin to saying that the experience afforded the resolution of a long-standing emotional conundrum, apparently for good. The consequent sense of equanimity has stuck with me and is something I am grateful for.

(I am certain I myself might have come to the same resolution through some other path; my sense from the communities I am in is that one reason people pursue this one is that such experience are very common. Whether through intrinsic pharmacology or some alchemy of set setting and expectation seems almost not to matter, IMHO.)