I have no idea what led me to that high of a word count, but I know it's not necessary to make the story that gargantuan. 100,000 words is a pretty good mark for a book, falling right in the middle of the industry standard range of 80,000-120,000 words. At least, that was the normal range the last time I checked.
But I'm not talking about all this just because I want to throw numbers at our face and shock you with my mathematical prowess. I mean, yeah, I do if only to prove that beneath this cool exterior beats the heart of a true nerd. I'm saying this because setting a word goal for yourself is one of those ways you can help set limits for yourself as you write, just like plotting your novel in an outline.
See, a novel an go on and on. There really is no limit to how big it can get. War and Peace had a word count longer than Tolstoy's beard. Marguerite Young's Miss MacIntosh, My Darling was even longer. In Search of Lost Time by Marcel Proust is about as long as both of these combined!
You don't need to write that much to impress people. Impressing people shouldn't even factor into the equation. It's all about quality over quantity. Think about some of the literary treasures of the world. I'm glancing over some of the titles on my bookshelf right now. Cormac McCarthy's The Road is a little under 300 pages. Michael Chabon's Wonder Boys is about a hundred pages longer. Justin Cronin's The Passage is among the longer books on my shelf running several hundred pages. It dwarfs Hemingway's The Old Man and the Sea, and many believe that work was a major factor in Hemingway winning the Nobel Prize. None of these guys have or ever will write as much in one book as Proust did.
So to keep you from chasing the word count dragon and its sweet, warm opiate embrace, I want to issue you a challenge the next time you set off to write anything from a novel to a piece of flash fiction: estimate how many words you think it's going to be, and then cut that estimate down by a third. And do it before you start jabbing your pen into your arm. Seriously, ink makes for sloppy track marks.