I played Stockfish on Lichess. It was a very balanced game from opening to midgame. My 23rd move - Qd6 turned the game around in a very unexpected way. In chess, "unexpected" is not always a good thing. Let's check out the game and see how things turned out.
First four moves gives us:
e4 e6
Nf3 b6
d5 Bb7
Nc3 Nb4
We have a beautiful start. With pressure from both sides.
Black's Bishop b4 attacks White’s Nc3, and bishop b7 points toward e4 and g2, eyeing the center.
White’s Ne5 puts pressure on f7, indicating a potential fork with backup from Qf3, with White's Bishop f1 attacking c4 and b5.
Next four moves:
f3 Qg5
d4 Ne7
g3 Nf6
h4 h5
Equal pressure from both sides once again.
The 16th move leads us to this
Qg5 c5
dxc5 bxc5
a3 a5
Bb5 O-O
Here we have a very tight position requiring trade-offs and sacrifice to break through. Here, I kept counting my pieces to make sure I wasn't short of material. It's my way of telling myself that everything is still under control.
Fast forward to moves 20 to 23.
Qd6 Qxc3
Qxa7 Bxd8
Rad1 Qxc2
Qb6 Rxd6
Here, I blundered Qb6. I desperately needed to take it out of harms way but... I didn't. A terrible oversight. How exactly did this happen? I can't explain. Just one of those blunders that makes no sense.
I know I should have moved Qd6, to perhaps b6? I began to make silly blunders from that point.
I've observed that once I make a blunder that costs me an important piece, the Queen, for instance, I simply turn off my brain and play passively. Why? Because I instantly lose interest. I'm yet to learn that blunders can be recovered from. This was visible in the endgame where I continued to blunder.
For instance, right here. Leading to a checkmate.
Good opening and midgame, terrible endgame.
All screenshots taken from gameplay.