Fortunately, I don’t suffer from writers’ block. I do, however, sometimes suffer from lack of inspiration. This manifests itself as wooden prose, ie stuff that is as dull as ditch water to read – doubtless because it was very difficult to write.
In such circumstances I find that the best thing to do is physical exercise of some sort rather than a writing challenge. Ideally, swimming, but if time is short or, like the present, I have a horrible cold, a brisk walk around the block will do.
Next time you feel stuck, try it.