A friend of mine told me about how she was having a rough day and missing deadlines like Greedo misses Han. I felt bad for her, especially since I've been having a pretty slow day myself with just a little fiction work and some editing on an article.
The slow days suck. Always have. Always will. It's like any other job. There's not a one that's all sunshine and puppies everyday. If there is, tell me. I'd love to apply.
The best thing I can recommend - and I know it's gonna really suck ass - is to simply push on as best as you can. Getting even a tiny bit of work might seem like nothing, but it's that much more than you had yesterday. More power to you. Make sure you're keeping the momentum in a forward direction. If you're regressing, then perhaps you really do need to take a day or two off to chillax.