Sometimes your brain just won't function. You're thinking about sandwiches, and fire, and cell phones, and deployments and video games. It's getting in the way of your writing. You sit down to do something, but you can't think of anything past the ever-flooding surface thoughts and nothing seems to come out right. You get frustrated.
Try out this: http://onetwofiver.com/write/. It's billed as a writer's warmup, and I can't think of a single better way to start any given blog post. If you ever need a good place to write a quick, disposable warmup to start your brain juices flowing, give One Two Fiver a shot. It really helps!