Writing is a strange mix of "working" at something without "forcing" it. The ideal of sitting down and reaming off perfect stories without pause...well, it hasn't happened in my world. It's something I have to study, to work at, to rewrite, to scrap and start over, to try new techniques, and so on. There is work involved in making a good story.
But, at the same time, you can't force a good story. There has to be an element of relaxing and just letting it pour from your heart. After all, it is "heart" that really grabs a reader. I don't mean mushy inspirationals; I mean the passion that is in you speaking to the passion that is in them.
This is why robots don't write stories. Why couldn't we just enter the formula for a good story into a computer program and have it type out all the next best sellers? Because robots don't have heart. They don't have passion.
And this is why you should not "work" so hard at a story that you start "forcing" it. Because writing is art, and art reveals the thoughts of the artist. If you are frustrated, trying to force a story, then your work will sound frustrated and forced.
So it's a balance.