An ounce of prevention is worth a pound of cure (even in metric).
I experienced over two month's of writer's block many a year ago. I did sit literally at my desk for hours, and can to this day accurately describe that desk. Its vision is before/behind my eyes as I key.
I have devised a scheme which I find is 90% successful in combating writer's block.
Do not finish your thought on page or screen. Make sure it is solidly in your mind (make notes if necessary) but do not write it down. If it's a description - don't finish it. If it's dialogue - don't complete it. If it's a line of poetry - don't end it.
The next day, start off with the phrase you could have ended with yesterday. Read the preceding page, slide into the phrase not used, and the odds are excellent you will continue on your way.