I would like to say a word about motivation. I have often found that when I hit my lowest spot, the point when I begin to wonder if I should just torch the whole project, my non-creative-harshly-realistic side swings in to save the day. First I tell myself that while it would be fun to set fire to something (a) I don't think that my computer is flammable (the most it might do is melt in a very unexciting fashion) (b) on the other hand my computer could be very combustible in which case it might explode and the computer shrapnel would disfigure my face (c) computer shrapnel in my face might be an interesting thing to write about but (d) I would have just burned my computer and would thus have nothing to write on.
Having been saved from burning my computer and all the hazards that go with it, I move on to the main motivation that pulls me out of the lowest of lows: my time investment. I am currently working on a project that I have been laboring away on for the past two or more years. I've reached the point where I have invested too much to give up. I dig myself out of my deepest ruts by convincing myself that it is worth it to keep working because it would be far better to have a lousy finished product than to have no product at all (besides two years of wasted time)
This is certainly not my only motivation and I agree that any time spent writing and honing the talent is time well spent. I just like to use this idea of time investment as the kick in the pants that I need to lift my spirits enough to lift my pen again. Once I'm there, with pen in hand, all the wonderful dreams, goals, and aspirations come flowing back and I'm washed back into writing. I've just learned that sometimes a harsh slap of reality is the jump start a creative mind needs to get it going.