I don't agree with this. For me, at least, there's this thing where, after I have written a thing and revised it a good deal, sometimes I can't change it.

Not that I don't want to, but further revision becomes circular and gets me exactly back to where I was. I've changed a passage and changed it and changed it and sat on it for a few weeks and then tried again and ended up with word for word what I started with.

Arbitrary constraints are good and helpful, though.