One secret to happiness in a writing career is anticipation. When you get behind (and I spend most of my time behind), all you have to look forward to is a slog and a potential sale. When you get a bit ahead, you have something coming out, you have something submitted, and your working on something else.
More productive writers have that feeling a lot of the time, but I do rarely. Aside from the book, I have a story coming out in Asimov's, and two more out looking for a place. Now, to really be ahead, I should have a story written for an upcoming workshop session.
But it's worth quite a bit of effort to get to this point, because it takes less mental energy to stay in it than it is to get to it. The writing brain is a delicate thing, and needs some care and feeding.
This is, I think, why some other people play the lottery. They want to always have something going for them. There's always a chance that the numbers will come out right, and something good might happen. All of us should try to make sure we've always got something going for us. We deserve it.