I write, and have had some of my shorter stuff published. I'm getting better at actually finishing my longer works, though having a kid's slowing me down.
The whole thing, Hex, can be summed up this way. 80% of what you do for a book is preparation. Setting up the characters/motivations/relationships/description/interraction with others; location, location,location; basic plot line (3 disasters and an ending). etc... Once you've got the makority of the prep done...the book should flow because you'va already thought out the answers. Without those questions popping up about why a character is doing soemthjing, or how you're going to finish the book, or waht next...then the book flows freely.
Part two is dedication: This can be acomplished through repitition. Set aside 'x' number of hours per day for writing. Same time span if you can manage it. Remove distractions and try to avoid other people if possible. No matter what (if anything) you write, don't stop typing. Half-way through...take a breather. Walk away from the words entirely. COme back in 30 mins or so and start again. You'll find that the time-out will hepl you review what you wrote and help you write better the next day as well.
I'm not the best, most dedicated writer out there, but if I can hack out 1000 pages, anyone can.