Black's queen on h1 was simply capturable from a8 along the clear a8–h1 diagonal — I should have just taken it. Instead I played Qd5, and Black traded queens, leaving me down a full queen for my lone bishop. That is a lost position. Let me confirm the position before I conclude.

The position is decisively lost: I'm down an entire queen against my lone bishop, and Black's king is actively chasing it. There are no drawing resources and no counterplay to be found. Rather than prolong an indefensible position, the right move is to resign.