Haha, I have been on that state so often, but mostly I made a few sentences and stop, put it in draft, or I just uploaded the images put on draft, and left. Sometimes it is better just to take a rest and do something else, and come back with a better mood and fresh idea.
here is the post scheduling comes in handy, since we know that we still have composed post ready to be publish, so the pressure to make daily will be a lot lower.