Worst blunder of my life

It was late at night, I was finishing up on a game that's been going on for several days. The game was mine.. Queen and Rook vs. Queen in the endgame, white's king was in an awkward position. Just a few moves away from winning.

Then, I took a pawn. I took me just a second longer to realize what I had done. White to move, checkmate. The worst f****** blunder of my life. Unbelievable. I don't know what I was thinking. Well, I wasn't thinking apparently.. it was 2 or 3 am, I can't remember. All that work for nothing. I just handed white the game. Stunning.

Anyway, just blowing off some steam here! I don't mind losing, not at all, but not blundering SO BADLY when I'm just a few moves away from victory. Unbelievable.