Just consider it a gift. 
(Yeah, missing a hanging queen and allowing mate in 1, all in the same move. And not even in time trouble. Ouch.)
Once during a tournament game, I was losing... or at least I was worse. I was worse because of minor mistakes I'd been making over the course of the game, about 3 hours.
Then he inexplicably blunders a rook. Like... just moves it to a square where I can take it for free... and as soon as he made the move I was the one who grimaced. I couldn't help it. In fact I was embarrassed because I didn't want to insult my opponent, but for about 60 seconds I couldn't hide my disgust. I was going to win this ridiculous game for no good reason.
Yeah, that sucks.
Although, in a somewhat perverse way, it's also the beauty of chess or at least of chess competition. The games are exciting to play partly because there's no guarantee of victory. There's nothing stopping either player from playing a really horrible (or really brilliant) move at any moment, and the game isn't over until the very last move.
That's almost worse than losing. Pretty close. I just roll my eyes, sigh, and wish I was playing a game that was challenging. I like having to struggle even if it means a loss. It's better than being served up a win on a platter.
I really need to check my moves more.