I’ve started playing more 19x19 games and I think that this most recent one is the one that went the longest for before any major screwups.
https://online-go.com/game/19606982 (My rating was technically 20k at the time of the match, but that was only due to a bunch of timeout wins so I’d consider myself 21k going into this game.)
Mistakes that I found after going through it quickly once on my own:
To start with, a big error I made overall is that I gave up 3 of the corners with very little resistance or attempts on my part to reduce the amount of corner territory gained by White.
Now for some specific moves:
Move 53: There was no need for me to play there since S3 and S4 were miai (I think that’s the right term?) for connection to begin with.
Move 221 - I’m not going to even try to defend why I didn’t respond to this peep; there’s a reason for the saying “even a moron connects against a peep.”
Move 223: Connect on the other side, dammit! I saved 2 stones at the cost of 6.
Move 225: -1 point to me for attaching an extra stone to what is clearly a dead group.
Move 243: Miscounted, thought I could force the group down to one eye.
Anywhere between move 251 and move 265: I feel like I should’ve at least tried to use M5 in attempting an invasion instead of trying to build an entirely new live group from scratch. Even if it didn’t kill anything, going from M5 down would’ve at least not cost any prisoners.
Move 273: See move 225 above. This does nothing but fatten an already dead group.
Those are just the really obvious mistakes; I haven’t done a thorough self-analysis yet. But even if I would’ve lost without making those mistakes (see my comment above about giving up the corners), at the very least there probably wouldn’t have been as much of a point difference at the end.