The first game below is a rather quick loss for me in a Caro-Kann, the mainline Classical variation; I think it can serve as a cautionary tale for other Caro-Kann players on what to avoid. My opponent rattled off all of the moves through around move 13 without any thought, showing a strong familiarity with the opening, and rather quickly played the best database scoring moves through move 16. At that point, I made a serious error and my opponent then played all of the strongest engine moves through move 26 - at which point White had over a +10 engine evaluation - showing precisely how to exploit my weaknesses on the kingside. For the Black side, this game is primarily a one-move lesson (that Black needs to play ...Qd5 at a certain point), but it also serves an excellent illustration for the White side on how to conduct an attack in this situation.
The second game, presented below, is a patient win for me in a slow-developing English Opening, in which my opponent starts with "The Sniper" formation then goes for a double fianchetto. The game is quite even for a long time, with a few small imbalances, and earlier in my chess career I would have been impatient to reach a draw, or perhaps try too hard for a win. Here I was able to think in terms of prophylaxis and in improving my own pieces until my opponent made a relatively minor error, which then allowed a critical breakthrough on the queenside leading to a won endgame. Patience is, I think, a feature of improved mental toughness. (One shortcut to this, I think, is also keeping in mind Bobby Fischer's mantra of "no draws!")