Sometimes, the words won’t come. Here’s my advice: accept it.
But don’t accept it and just stop. Accept it as a symptom. Maybe you need more sleep. Maybe your plot is weak, and you need to figure out how to fix it. Maybe a problem at home or school or work is weighing on you, and you need to address that.
I see, far too often, the advice to “just write”. But if you can’t, that doesn’t mean you’ve failed. It means you have other priorities. If you wait for everything to be “just right” because you can “just write”, you might never get around to it. That’s a different thing than trying to just write when things are quite wrong.