It was a last game of the tourney, I was +2 and got paired with 1900 rated young guy.
He had White and played Ruy Lopez,  here is the game.  I went for Marshall attack, he accepted. First surprise – he played 12. d3, and then 15. Re4, not much familiar to me  (I found one blitz game I played against it), except that I know I have to play 15…Qf5.  He then played 16. Bc2, actually not the best move,  and I think it was the critical moment.  Would I play 16…Qg6 with excellent stats and any engine suggesting it, I would never have problems I got in the game. My light-colored bishop would be “strong and free” (like “The True North” in our anthem) on f5, and dark-colored one would never get exchanged. I wanted to use a non-stable position of his rook,  21…g5 was a good idea, but being implemented one move earlier than needed became the bad one.  I didn’t have any attack and my attempts to get one only made the position worse. His pressure intensified, the position was bad, also I started to get behind on time, having ~13 minuts vs. his 18 when I blundered on move 42.  The rest was clear and I resigned on move 47, with  the perspective of losing queen for knight.
Of course, I was upset, losing in my favorite opening, which I played more than 100 times blitz  (but only once OTB, by the way).
The total result was some consolation – +1 and ~1950 performance rating.