It’s what you say on those days when you’re exhausted, sick, emotionally drained. The last thing on your mind is creating something. You’re pretty much focused on surviving.
You have two choices. Dig in and see what your tired frame of mind can produce, or you can rest up. Neither is the right choice every time.
But if you’ve got a scene in your novel or screenplay where a character is exhausted, sick or emotionally drained, maybe it’s the right choice right now.