You had this won three separate times, and every time the winning move was a check or a capture — and every time you played the quiet move instead.
The same knight jump, Nxg6, was on the board for two of those three turns and never came off it. This is the conversion habit in its purest form: over +2, the question stops being "what's better?" and becomes "what's forcing?"
14.Qxf4 — the check comes before the recapture
James had just taken your bishop with 13...Nxf4, and the natural reply is to take the knight straight back. But the check jumps the queue: Ba4+ Ke7 — the king can't castle now — Qxf4 Nxa4 Qxa4, and you are +3.9 with James's king marooned on e7 for the rest of the game. Your 14.Qxf4 is not a bad move; it just lets him off the hook, and +3.8 became +1.2. When you are up material and a check is available, the check is almost always first — it costs nothing, and it takes squares away before you commit to anything.
17.c3 — Nxg6 was winning; c3 was a pass
You had built this beautifully. The exchange sacrifice 16.Rxd6 was the right call — it kept you at +2.8 with your knight on e5 and bishop on b3 pointed straight at James's king. Then, after 27 seconds, you played 17.c3. The move that finished the game was Nxg6: Nxg6 Qxf4 Nxf4, the queens come off, and you are +2.8 in a technically won position. Instead, a quiet pawn move in a position begging for a forcing one dropped you to -1.8 in a single turn.
18.Rd1 — the same move, one turn later
James let you straight back in with 17...O-O, and Nxg6 was winning all over again — identical jump, identical idea: Nxg6 Qxf4 Nxf4 and it is +2.9. This time you spent three seconds and played 18.Rd1, and it went to -2.3 for good. Notice the two clocks: 27 seconds on c3, three on this one — the same miss slow and fast. That tells you it is not time pressure; it is what the search is hunting for. When the eval is already big, it has to be hunting for the forcing move, not the tidy one.
Profile check
Same mistake as the Dutch you lost the other day? Yes. There you grabbed a pawn while a whole piece hung; here you passed on a winning capture three times over. The move changes, the habit does not: the hand reaches for the natural move exactly when a forcing one wins. Confirmed — and it is now the single thing standing between you and beating James.
What to drill next
- This exact position — play it out from move 17 as White and find Nxg6 before you touch anything else. Beat the engine from here three times running.
- Convert a winning position — these puzzles never ask "what is best," they ask "what ends it." That is the muscle that was missing today.
- The in-between move — the Ba4+ you skipped on move 14 was a zwischenzug. Take the free check before the recapture, every time.
Over +2, before your hand moves, name every check and every capture — the winning move is almost always sitting in that list.