I can see the finish line, and is it ever depressing

I don't often indulge in one of those writers-writing-about-their-writing posts, and I promise I'll try not to overdo it, but I have to kvetch. If you had asked me a few moments ago how long I'd been working on my novel, I'd have told you, "Three years." But I just checked. I wrote the first version of the outline on 4/27/03, and I finished the earliest version of Chapter One in June, 2003. I've only been at this two years! It just seems like three. Here's the first paragraph from that very first outline: On Earth, it would be the 1960s. The action takes place two years following first contact between the Brakans (five-foot tall birds whose wings have evolved into arms/hands) and the Benevolents (classic aliens with a twist: scrawny, big-headed, big-eyed aliens with opalescent eyes and a mouthful of sharp pointy teeth, who carry themselves with all the supercilious arrogance of the British Empire at its peak. Benevolents have a desperate love for all things human, and have submerged their own culture in favor of a melange of human pop). It is the dawn of Empire for the Benevolents; they are currently holding tense contract negotiations with dozens of ‘Useful Planets’ (their phrase), in order to expand their wealth and influence. The novel's title back then: Freedom Fighters. This is on my mind because I finished the second-to-last chapter today. All that's left is the epilog. I suppose I ought to feel a sense of grand accomplishment (this thing is HUGE), but instead, I'm depressed. Is there a post-partum depression for novelists? Or am I sad because the material itself is sad? It's certainly not a 'what do I do now' sadness. The edit will keep me busy for several months, and I've long neglected my short stories in order to focus on the NiP. Time to ship out another eight or nine shorts and perhaps rewrite the few that need serious rehabilitation. If I want to start a new novel, I have a good idea where to go with the sequel, AND this morning Karen gave me a nifty idea for a whole new world to inhabit. Since that idea will take a good bit of research, I could waste a few months reading books instead of writing a word. Did I mention I'm writing a tragedy? I can't help but think I feel guilty for doing this to them (my characters). If this were metafiction, they'd rise up off the page and give me a dose of my own medicine. D.