Another reason is that I think, with time, I can always make things better. I can think something through more clearly. I can find a better turn of phrase. Eliminate unnecessary words. Read everything that has ever been written on the topic and start again.
I now know that letting too much time pass, or engaging in more than a few rewrites, gets me into dangerous territory: a place where I care more about trying to achieve some kind of imaginary perfection than in releasing whatever it is that is trying to come through me. And the result, inevitably, is that I go in circles until I ultimately come to a suffocating and stultifying dead-end.
I also know that, lately, something important has shifted. Because what I really want now, more than finding just the right word or insight, is to be in relationship with others–my readers, in this case. And that requires letting go.