This is such a nuanced, multi-faceted question. I realize you, kind reader, want to know what aspect of fiction writing—specifically historical fiction writing—is the most difficult. Is it the research? Is it finding just the right detail that will make a reader feel as if they’ve traveled back in time? Is it cutting and slashing all my darlings in the final edit? No. That isn’t where I get stumped. Oh, don’t get me wrong, there are bumps! And lots of them. But to me, historical fiction writing is a puzzle: my fictional narrative + historical something (event/date/fact/person—it all depends on the story) + editing = a cohesive product in which all these elements fit together seamlessly. Each of these pieces have their own unique purpose, as well as their own unique difficulties. I revel in placing all of them together, time and time and time again, through edits, rewrites, and more edits. Constantly resorting and reworking until it’s right. Until my word puzzle is a readable manuscript. It’s hard, but it’s not hard hard.
No. Hard hard is being asked to write something on-the-fly, that will come out as gracefully and effortlessly as my final products do. (I understand that’s totally subjective, but work with me here.) I’m used to multiple drafts. Multiple nasty, messy drafts. Writing is a messy business, boys and girls! We novelists don’t just vomit out finished products. (Well, Stephen King might. He’s pretty brilliant.) But I don’t. I claw at words, tearing each syllable out of my soul as I struggle to find the perfect sentence in both nuance and cadence. So, when I’m asked to write an obituary (true story) it’s very hard to explain that while I am indeed a writer, I’m a fiction writer. (Which, side note—may make a person’s life more palpable if they were generally disliked—but…well, just don’t expect me to give you anything insightful, or even reverential, for this. I’m not the one.) And while I am a writer, I don’t just produce a finished product on-command. I need some time. (Again, messy, multiple drafts. Trust me, obituaries take some thought—or at least, they should.) Same goes for a eulogy (also, true story). Oh! And, just for the record, obits and eulogies should be written by someone close to the deceased…someone who liked them. Just lettin’ ya know. (And if you can’t find anyone to fit this bill, then yeah…a fiction writer may be your best bet.)
So, in short, I would have to say, the hardest things for me to write are things expected on-the-fly that are to be insightful, inspirational, or reverential. Now, if you want sass, snark, and a highly inappropriate bawdy story <raises hand>.