Phoebe mentions a new and potentially interesting angle that helps clarify my ambivalence about Lena Dunham, who I cannot seem to stop writing about: part of what grates is the assumption of a persona in which attaining the trivialities of adulthood are to be celebrated as significant milestones (there is perhaps a Judd Apatow/Seth Rogan connection to be explored here); it grates because the person herself appears to not have any of these problems, but one can very rarely see through the art to the life. I asked a question about the evidence for this public persona/private personality split in the comments, to which Phoebe responded.
Part of my reason for wondering is that, as I've been thinking about it, I tend not to assume that people who have successful creative lives might otherwise qualify as 'having it together' in all meaningful senses. Amongst writers, for example, one need cast about no further than Scott Fitzgerald or David Foster Wallace to see the type in practice (Fitzgerald, in particular, wrote some perceptive essays about how to make money as a writer: an excellent professional but couldn't hold his life together for anything, which he then mined for more material). On TV, the rise of the auteur also gives rise to the borderline-insane genius; Dan Harmon's flameout as showrunner of Community is a good example: three seasons and more episodes than Girls, of mostly high quality, and then ouster after the difficulties of getting along with all the business-side people became too much. In movies, we can begin and end with Woody Allen, though I will also suggest Roman Polanski as a similar case. In the excellent Cheers oral history, there's a section on Kelsey Grammar's drug addiction, and how he was a complete mess offstage, but able to snap into place once the cameras were rolling.
In other words, examples where the art implies nothing at all about the life seem legion. That's not to say Dunham is in this category, or that we could possibly know, just that the "having professional success" and "having it together" categories do not seem to imply each other.