This is an actual mental issue with good chess players called chess blindness. Your brain gets overwhelmed by the possibilities of a chess game. This happened to Magnus at one point that he blundered constantly. It's a real thing, look it up
I can't comprehend Chess

Of course studying it and doing it are very different, Practice playing more and you will get better at playing with all the highs and lows that come with it, other than, as blazorbyte writes, chess blindness can happen to anyone, of course more with novice players

Same here, watching John Bartholomew's 'Climbing the rating ladder' series and everything seems so obvious yet in a real game I don't see half of what I see when watching. Started playing 5 | 5 instead of 5 minutes the past few days and it seems to help.

This is an actual mental issue with good chess players called chess blindness. Your brain gets overwhelmed by the possibilities of a chess game. This happened to Magnus at one point that he blundered constantly. It's a real thing, look it up
Yeah, that may be true for good players, but not sub-900 ratings. Take it slow, do tactics ad nauseum, and play play play. Don't worry about the wins, and analyze and understand your mistakes that cause your losses; don't pine over your wins, they are not that important.

I've also heard of this referred to as the "illusion of competence" in a learning context. It's basically where you read something in a book or and think you already understand it, but when you are tested on it or need to apply it, you completely blank. Yet when you look at it again in the book, you can easily recognise it and feel like you know it already.
It's the same in Chess; whether we're learning tactical motifs, middlegame concepts, endgames or opening theory, it's easy to read it and recognise it when it's spelt out for us in a book or video, but entirely different when we're in the middle of a game oourselves. There's no prompt for us to think about what we've learnt, and it's easy to default to what we've always odne in the past.
I recently realised that it's become a problem in my CHess progress as I learn more but keep When I was stuck at 700 Rapid, I realised it was the biggest problem stopping me from progressing. Even though I was learning about tactics, basic opening theory and strategic ideas, I just couldn't spot them in my games and I would allow these issues to make me lose games. Here's some of the things I did to work on it:
- When analysing my games, think about whether the concepts I've recently been learning about have popped up and whether I could have applied them to gain an advantage. For example, I was missing lots of forks, pins and skewers when I was starting. I knew what they were, but just couldn't spot them. Focusing on them during my game analysis helped me to see how they showed up in my own gmaes.
- I tkae my mistakes and positions where I didn't capitalise on opportunities and put them in a training database on Chessbase to go over them again as much as I need, to get practice at spotting them in my own games. It helps because they're real positions that I've seen before. You could also do this with CHessable, I think.
- For opening theory, I stopped just trying to memorise moves, and focused on understanding why each side makes each move. I'vm building my opening repertoire through trial and error so I can understand what happens when I don't make the best move every time. After each gmae, I look at where I feel where I was no longer in book and look at what the best move should have been. Once I understand it, I stop there, just adding one move at a time to my repertoire. That way, when I face the same position again in the future, I'm not just playing a move because the book says it's the best one, but because I'm trying to control a certain square, slow my opponent's development, etc
I think it's always going to be somethnig we struggle with as Chess players because there's simply so much to learn and master. And we make mistakes - there'll be lots of games and positions where we're struck by chess blindness and can't see the bleedingly obvious things on the board that we've already grasped before.
I love chess, watching videos, playing, studying openings and moves and setups, and when watching people play, I can see what moves are best and what moves are blunders on both sides and why. But when I start playing, it's like my brain shuts down and I go blind. i can't see any moves at all, make constant mistakes and stuff, can't see more than 1 move ahead. Is there like a mental block some people get? or choice paralysis or something? I don't understand what's happening. Or if It's just a brain wiring thing