Flow. It feels great. I'm a writing god.
Other days, not so much. I struggle to put two words together, and when I do I wrestle the impulse to delete one of them. The scene in my head is clear; the scene on paper should be taken out back and shot, then doused in gasoline, and . . . *blech*--it's not even worth burning, just throw it away. But I don't throw it away. I soldier on. Because when you find yourself going through hell, it's a bad idea to stop and setup camp.
Everyone I know experiences both these states: some Fight more than Flow; others Flow more than Fight.
I find I produce my best work when . . . I'm writing. Sometimes I go back and read a scene that Flowed, and it's awful. Other times, I dread reading a scene because I fought with that piece for hours or days, and it works with only minor tweaks. Of course, the opposite is true as well.
So whether you feel like doing something or not, roll up your sleeves and get to work. Some days you'll enjoy going with the flow. Other times you'll struggle against it.
Come heaven or hell, as long as you keep putting words together and working scene after scene you're going to make it.
* I totally need four or five of those Works in Progress cones to put around my desk while I'm writing. The picture was taken by koalazymonkey and can be found on Flickr.