Definitely more when I've had less sleep. But for me personally, I can go a few days with really good fluency and then the next few days, I can barely go more than a few words without blocking. I also stutter a lot more when I read out loud, which is frustrating because then people think you don't know how to read, which sucks. I guess it's because when I'm reading, I can't change the words that I know I'm gonna trip on since the words are right in front of me.