I think it depends on why you’re suffering from writer’s block.
If it’s because there’s some problem in your plan for the story that you can’t account for, then all you can do is continue to think about it until you solve it, as if you try to write earlier your subsconscious will be completely paralyzed by the contradictory orders until you do solve it.
If it’s because you’ve just been over writing and your mind is getting tired and repetitive, then the solution is simply to do something else for a little while. Usually I only need about five minutes.
Finally if it’s because I simply can’t think of anything, then I make sure I have enough laid out to know what I should be writing, and at that point I just write something and it’s usually apt, or if not, I have something to correct and work with.
I’m a very structured writer. I like to think of pieces of writing as an engine or a building to be integrated and designed carefully.