I think all content creators face this problem, what works for me is that when I have a day of great inspiration I write down the ideas or make a draft of the idea, this allows me to have several topics when I don't want to write, on the other hand I think that just as the muscles get tired the brain tends to get tired too and you just have to get away from the pc for a while and let the brain rest for a while, running is a good option.