From a place of wrath and tears

In his You Tell Me, Nathan Bransford asks: 
What is it about writing that makes people put on the blinders and fail to recognize their limitations and makes the talented unable to recognize their own goodness?

After 195 comments we had in the answers:

1)    lots and lots of: writing is subjective and personal, tastes differ. It's really no different than any other art (painting, music,...). Then add: but what's good enough to get published might not be so subjective, but then as hanna@14th-10:38AM pointed out and Dave@A Writer's Look@14th-10:43am expanded, you also have to take into account that bad writing gets published and sometimes sells way better than good writing, and that Nathan gets cranky when you push that stream of thought to its limits (only $$$ matters to the market). Anonymous Bill@14th-12:29pm sidesteps this nicely, and concludes that what's important to the discussion is not that bad writing gets published, but *why*: "These are the surface characteristics, not the true nuances that make for lasting success. And recognizing the less recognizeable, IMHO, is the key to differentiating the amateur of transient brilliance from the lasting professional talent."
2)    Mentions of the Dunning-Kruger effect abound, which IMO sort of comes down to "we're basically unknowable about the things we don't know so we don't know but naming it Dunning-Kruger makes it sound posh".
3)    Jaime@14th-10:52am encapsulates what others said before: it's language, everybody uses language, so it can not be difficult. Add trent@14th-10:37am's that writing doesn't need a great deal of capital before you can start. Add to this it's a learning process (you can always learn more and better language), everybody "thinks" s/he's a good writer until they try. Also, not everybody is taught what good writing/literature is, which sort of ignores the whole point of the subjectivity of "good writing" in #1 (. Though I agree that benchmarking is an important part of the learning process.
4)    Some of the fingers pointing at subjectivity do not limit it to "good" or "bad" writing, but how basically you can compare titles. An apple is not a pear, though both fruits, right? And yet our so low-cost writerly tools (trent, above) only help to create deception; as Kerry Gans@14th-1:43pm puts it: "Maybe because my typed Word document looks the same as everyone else's typed Word document [...]you can see that you can't jump as high as the NBA guys [...] But my words typed on a page look pretty much the same as JK Rowlings'".
5)    Also, abundant variation of the theme "there's always idiots". Our egos get in the way of clear thinking. Or more softly put: everybody likes their baby, even if it's a misshapen heap of flesh without a brain. Writing creates a high, and you need your distance to be a good judge. Nancy@14th-7:02pm phrases it nicely with "Most writers don't realize they have substituted quality for euphoria in the act of creation. It takes years of practice and learning to discern the difference. What we see as a talented writer is one who constantly goes through this process of discernment, and probably has a worn out delete key." We delude ourselves links nicely with:
6)    Imagination (Travis Erwin@14th-1:36pm). To write we tap into our imagination, and it's a land where we're kings and live in huge sprawling palaces with 100 bathrooms with golden taps and not once in that bit of fantasy we stop and think about who the hell is going to keep all those bathrooms clean. As C.J.Atsvinh@14th-1:46am puts it: "when we dream, man do we dream big." From this naturally follows what Ghost Girl@14th-10:46am says: "it's kind of like hearing our own voice; it sounds completely different outside of our own head." And James@14th-12:12pm links it closer to language: "People imagine writing is especially easy because it is the only art form that is expressed in our minds - or seems that way. This creates the illusion that we have created what we are reading", and Brant@14th-1:52pm continues in that line: "That process translates into me having a qualitatively different experience when reading my own work than someone else will. For everyone else, the text has to stand on its own merits." Ink@14th-3:20pm elaborates the idea that words are at the heart of a work's subjectivity: "part of every text comes from the reader, from how they translate these symbols into a vision they see and hear and feel [...] for the writer, we already have the vision in our head. We have it there as we write, or even before we write. "

IMO, it's not simply that words can and will be interpreted by the reader even when the author has great skill or craft or talent or luck in guiding the reader's eye and mind (go too far on that post-modern path and you'll soon be proclaiming the author dead, and trust me: not where you want to end up as writer). That everyone carries their own experiences in words with them is only part of the problem.
But words are the tools of our mind, not simply of our imagination or memory. We think in words to define our reality, it gives form to the formless reflections of light that fall into our eyes. And while through imagination we create a new reality with words (as writers and readers we experience how that works), we often fail to see that even the real reality in which we sit behind the computer writing is in a way a construct of our brain (but let's not go off into the deep-end of solipsism). We easily get fooled by our own high because what we write at that moment simply *is* sublime. By feeling/thinking it, we make it so, to us at least. And without drifting off into solipsism: who is to say it isn't?
And that's why it's always such a good advice to put something in a box or drawer for a while when you think you've finished. Not simply because somewhat later the high will have worn off, or we'll have learned new tricks, can sift out errors we've newly learned to identify, but also because our words themselves, the meanings and associations and experiences behind them, have changed. When you look at your creation again after a long time of doing something else completely, it will be with almost literally new eyes.
And then, of course, the trick is to keep that distance, not get sucked in by your own imagination or high again, so that you may actually see things for what they are...