But in fact, your block might be telling you that you're exhausted, or stretched beyond your ability, or that you need more time to work something through. It might be telling you you've found the wrong thing to work on, that maybe something else would appeal to you right now. Some writers overcome their blocks by putting down the piece they're working on and picking up something new. Others leave it alone completely, and let the piece rest for days or even years, until they get a new moment of inspiration.
The most important thing to remember about the block is that it provides you an opportunity for silence. Time to sit with the feelings of uncomfortableness, while nothing is coming to you, is necessary for growth. That's easy to say, and extremely hard to live with, though. No one feels good about writer's blocks. Another thing to keep in mind is that if you don't think of it as a "block," but as an opportunity, you take your inner focus off the endpoint, the goal, the outcome, which you're straining towards, and redirect your focus toward what is actually important, which is why you're writing the piece in the first place.
When you rush toward an externally-motivated goal, you tend to be disappointed when the goal isn't reached, either at the pace you have assigned to it, or in the way you hope it will manifest. The writing block could be trying to tell you something very important about yourself; let it. Listen to what happens when you can't write. Don't anesthetize it. Don't deny it. Don't be like F. Scott Fitzgerald or Hemingway and go into a self-induced panic, compare your manhood to the amount of words you've gotten onto the page, and get out the gun. It's not worth it, and you create nothing but misery for yourself when you think like that.
A worthwhile resource, the only one of the many writer's block books I used to have that I kept, is by Victoria Nelson (On Writer's Block). If you ever feel like you would like to understand what causes this feeling of being stuck, and would like to change how you think about it, this is a book I'd highly recommend. Another one is If You Can Talk, You Can Write, which can get anyone past any writer's block that isn't based on psychosis, I promise.