My pre-tournament tipping may have put a hex on Magnus Carlsen, as he lost his first round game in the Grand Slam Masters to Caruana. He was of course unlucky (in the chess sense), as he was pushing for victory for most of the game, only to come unstuck when Caruana played a double edge sac in the ending. Often when a game is going in a certain direction for quite a while, an surprise move can often upset a players rhythm, and bad things can result.
It turns out I had a similar experience a few hours ago. Except I was defending an inferior ending, where a loss was just one step away. The reason I got there was that I had played a game that was a mixture of inventive ideas and incredibly poor execution. At various stages I gave up a pawn, lost another, had 2 pieces for a rook, simply blundered a piece, and after all that ended up in a rook and pawn ending down a pawn. So I defended and defended, as my opponent edged towards victory. However he missed a couple of key ideas, and right at the death, blundered away his advantage. After a few more moves we reached King v King (possibly a first for me at long time control chess), after 4 1/2 hours play. In my case it wasn't one surprise move that saved it for me, but just the frustrating defence I put up.