Lost to Dasha with a terrible starting hand (by turn 10, I had no Ogres, one Blade Mage, one Destroyer for 7, a Chimera for 6, and one Dasha, which didn't seem to draw any spellboost cards), because my own hand was even worse. Before that, two Sapphires were exchanged in a desperate move. In the end, the opponent played an Enhance-Golem-Storm combo and simply overwhelmed me with Golems, while I sat there with three Accelerations like an idiot.
But I was most upset not about this, but about the decisive match against a Shadow player, which I messed up myself: sitting at 9 health and knowing that the opponent probably has Aisha, I first destroyed my only Mystic, and then realized that it was, damn it, a Ward that would have saved me. I would have won the next turn. Don't do that.
To sell my soul