Lack of sleep means your brain lacks the functions it normally does. What that means is, aside from the basic things like talking and walking, we can't think and consider the things we say or do properly. Just like a person who's high on weed. And even if you 'qadar' your sleep during the day, it doesn't help much and not to mention it being unhealthy.
It's not just the physical effects that bothers me though. I don't know if it's just me, but due to my lack of brain functions, like filtering of whatever it is that I said today, people are condemning me for it. Even my close friends. In normal situations, I'd consider the things I say to be well... normal. But suddenly today, I'm 'mean' and 'straight forward'? Trying to understand what these people meant. Maybe it's just a way for them to annoy me. Or maybe they really meant. And maybe I was being cocky and obnoxious. Whatever it is, I wouldn't know because I can't think properly thanks to my lack of sleep.
Not sleeping? Bad idea.