You attacked on the wing where the exposed king was your own.
The opening was not the problem. At move 11 the Classical Caro-Kann had you at +0.2 with everything developed and the king castled.
11.h4 - the attack begins and a2 is left hanging
One minute forty, the longest think of the game, and it went from +0.2 to -1.9. The board fact is simple: h4 leaves a loose pawn on a2, and your king is on c1 next to it. Kb1 was the move, and it fixes exactly that problem, because the king on b1 defends a2 itself. The line runs Kb1 Be7 Ne5 O-O Qe2 Rfd8 Rhe1 Nxe5 dxe5 Nd5, still +0.2, with the h-pawn push available later once the king is tucked. A long think that ends on a flank pawn push and drops material at home is the same shape as the two and a half minutes you spent on 20...Rb8 against James on 07-23.
13.h5 - a third wing move with the king already under fire
Forty-two seconds, and -0.7 became -3.5. The board fact is that h5 gives Black Qa1+. Qb1 was the move and it works by offering the trade: Qb1 Qxb1+ Kxb1 h6 b4 Nd5 Ne2 N7f6 Bg3 Ne4 leaves you at -0.6, a pawn down in a queenless position instead of a king hunt. Your notes have this the right way round for attacking, that queens are your best pieces when their king is stuck. The converse applies here. Defending, the queen trade is the escape.
14.Qc2 - the square that leaves a1 free
Eighteen seconds, -3.5 to -5.8. Both Qc2 and Qb1 allow Nb3+, so that is not what separates them. Qc2 also gives Black Qa1+, while Qb1 gives Black Qxb1+, which is the trade again. The line Qb1 Nb3+ Kc2 Qa4 Kd3 Nd5 Be3 Qb5+ Kc2 Qc4 holds -3.5: a bad game, and a game. After the move played, 14...Nb3+ arrived defended by the queen on a2 and there was nothing to do about it.
What to drill next
- The position before 11.h4. It is level, your king is castled, and the whole question is which move comes first. Hold the engine to level from here three times running.
- Defensive move puzzles, for finding the move that holds rather than the move that continues the plan.
Before attacking, check the squares next to your own king.