I love writing. I love creating stories that tease the imagination and hopefully come alive for the reader, but I write slow. I can offer a lot of excuses but some are very legitimate, and I think buried in all of these reasons there might be sound advice for others with this snail problem.
First, I get bogged down in research. I'm always questioning myself when it comes to historical references. So, while I'm working on the next sequel to The Rose Hunter, I find myself once again searching for those details that will make the book resonate, will make the book believable. The problem is that there are a lot of details that could be included. The story will begin in 1213 AD (Oh wait, that's not kosher any more. I should have said 1213 CE but when I write the story I will use AD because that's how they would have referred to it.) I digress. My best advice to you as you research is to keep it simple. Truly, you don't have to include all that happened in a given year or time period. Find something that will accent your story and give it flavor without overwhelming the setting you've chosen. Or perhaps, a main historical event is the backdrop for your story. Once again, see what you can do to narrow it down. Think about the civil war for example. A lot of battles were fought, a lot of political intrigue took place. You don't have to include it all.
Second for me is time management. I work a full time job plus. I teach so my forty hour work week is typically at least a 50 hour work week or more. I live in the country where my husband and I are finishing out another cabin so the weekends include helping him do things like staple up insulation (that's what I did yesterday). Then of course, time has to be set aside for the mundane things like cooking, cleaning and other chores. But I had someone trying to teach me guitar one time and he had something very profound to tell me. He said, "Practice everyday, even is you only play one chord for a split second. The trick is to put that guitar in your hands everyday." Writing is the same way so I try hard to open up the manuscript and write each day even if all I eek out is one sentence because at the end of the day, I'm one sentence closer to finishing the book.
Another setback for me is my darn internal editor. Try as I might, I can't seem to turn off the internal editor as I'm writing. This really slows things down. On the other hand, my rewrites aren't as extensive as they would be if I just wrote without editing.
My writing habit also slows me down. I don't outline. I'm a pantser. I can have a great day where I draft a whole chapter without blinking an eye but as a pantser, I tend to write myself into corners. That ending hook is great but then where will it lead me? So then, it's stewing time. I have to let the idea percolate. In some cases, like this last book, the idea brewed for six months before I settled on a direction that was plausible. Yeah, I should outline but the reason I write by the seat of my pants is so I don't get bored. If I know the ending already, I'm less likely to finish the book. I want to be just as surprised as the reader.
My vivid imagination doesn't help either. I tend to have more than one project going at a time. At present I have three books in the works. (Well actually five, but two have been rather dormant so we won't count them). I'll write on one until I hit a roadblock then go to another. The problem with this is remembering what I wrote when I come back to a storyline I've let sit for a while. To help, I try to have an ongoing outline for each story. As I write the chapters, I try to outline the main ideas. I still have to reread just to get back into the book but the outline does help keep facts straight.
And last, but not least, there's the physical aspect of writing. My eyes get tired. There are some days I just don't want to turn on the computer. There's nothing I can do about this except give my eyes a break now and again. Don't sit at the computer at long periods of time without getting up and moving around. It's not healthy for your eyes or your body. So - I tend to write for 15 - 30 minutes and then force myself to get up and take a walk. I have the most fabulous place to take a walk so really, it's not an imposition to move away from my desk.