I feel like my biggest weakness (among many...) is knowing when to push pawns. When I review the games, my opening is normally solid but in the middle game I tend to lose ground by pushing the wrong pawn, breaking/keeping the tension or moving a3/h3. What's the best way to get better with pawn play?
This is an amazing course for working on pawn play: https://www.chess.com/lessons/every-pawn-structure-explained
I am 2000 rapid chess.com, but am looking at starting to play OTB classical in 2025. Even in 10 | 0 games I sometimes find myself losing focus and making errors I wouldn't normally make. What methods are there to specifically train / improve chess stamina in order to maintain a higher focus for longer period of time?
I think the key here is simply practice. If you mostly play blitz, you'll be good at blitz. If you mostly play rapid/classical, that's where you will be strong. Good luck!