I feel like it's like speed chess and not normal chess. You have no time to think till after the game, you just have to do and trust your gut.
The slow brain is what exhausts you.
e.g after recalling/killing enemies/dying you have like 30sec to look around map and think what you as team want to do / achieve and how to do that
It depends on the stage of the game, but generally when enemies are around, then you may don't have time to think.
I've never played competitively, though I did get to about top 3000 in North America. Thanks for sharing!
Matches where e.g we lose early game and have to come back somehow by avoiding commiting mistakes hard and somehow catching off somebody from enemy team could be exhausting cuz you're basically balacing on the edge for 30min :P
30 seconds is infinite in games like that.