So, writers' block is pretty rare for me. While this sounds like a good thing, it has some downfalls. One being that when it happens, it kinda freaks me out. I get worried my creativity won't return.
Personally, if this happens, it usually means I'm burned out. I was world building too much, too many totally different scenes, or overall writing too much. If this happens to you, my advice would be to take a short break from RPing. Few days, maybe a week. Give yourself a guilt free chance to refresh.
When it comes to just having some days that are more difficult to write than others, that is probably an issue we all have. So, you aren't alone! Some days our words just flow better. If it seems dramatic, reflect on your day. Did you not sleep well? Are other thoughts distracting you? Was work extra annoying? And so on... Try to be kind with yourself about it. As long as your partners are understanding and okay waiting, take your time.
I'd also like to note that not every post needs to be everyone's 11/10. Sometimes we just need to send a "meh" post to push things along to get to a more inspiring moment. I know I write quicker and longer when I'm really interested in what is going on compared to dull moments. Sadly, sometimes RP can feel like a grind, but that is why inspiration is important.