I used to think I was a fast writer, but I've realised that only applies to a small percentage of my poetry, and I have a large collection of failed attempts. A good deal of the writing I have been doing lately involves going back to my files and revising the old poems, the ones where I feel there is a spark that I really want to turn into a successful poem, even if the first attempt was pretty dire.
The worst advice I ever read was not to revise. Granted, this was in a book which was more about writing poetry as self expression/therapy than about writing as literature. Even so, I can't agree. The author seemed to think that to revise was to deny the initial emotion that led to the poem. In my experience, the opposite is true. I remember an occasion when I took a poem to my small workshop group and was met with somewhat blank looks. "What are you trying to say?" one group member asked. I launched into an impassioned defence/explanation of the poem, and she replied "well, why didn't you say so?" And so, I revised the poem so that it did say what I intended to say in the first place.
And that, in my view, is what revision is all about. To make the poem more of what it set out to be.