It is obvious, that you cant´t play your best chess if you are tired, unwilling or depressed. Brains simply are not in a good working condition.
Playing tired
I just won a game, and it's late morning, proving yet again that time of day is very important. I'm going try to stop playing today completely and leave it 'til late morning tomorrow... What do I do now though :(
Kastike said: "Brains simply are not in a good working condition."
I heartily agree. I'm looking for an electronic transplant - they can do it with hearts now. Come on all you potential medical researchers, stop wasting time on here, stop playing chess, and devise a better brain!

It's harder to calculate and be consistent when you're tired. I'll usually avoid a blunder on one turn only to play it anyway a few turns later!

I have the same issue, if i get less than 6 hours of sleep I can't play, I miss obvious moves, when I know i'm this tired I just play against the computer and practice openings, or watch some learning videos on youtube

I had signed up for a tournament once. But due to my insomnia, I got ZERO sleep, plus a two hour drive to get there.
I played terribly. Even losing to a 12 year old fat boy. From a perfectly salvageable endgame.

Exactly Evenflow332. I'm 1200ish on rapid, which is what I'm focusing on, but last night I lost so many games in a row because of stupid blunders even I would be able to see. Like stupidly moving a bishop right in front of an enemy pawn.

https://chessmood.com/blog/stop-playing-chess-when-your-body-does-not-want-to Definitely you need to read this article!

don't play when tired. And why the bump, dude
This post has been getting bumped since 2014, no need to be rude when no one else was.

Don't play when you are tired if you want to win. I experience bad days when I haven't got enough sleep, so if you want alpha brain sleep enough.
Please try not to knock me down while you are driving when overtired.
Or perhaps get some sleep before taking to the wheel.