0 that could easily have been 1

This position occurred in the club match today, where Black's pieces were led by a team-mate, Peter (first name).
Black is two pawns up and has an initiative against White's vulnerable king (honestly, if I had been White, I would have resigned here since it is a clear -+), yet after 1..g5 2.fxg6 Rxg6+ 3.Kh3 Rxg2 4.Qxg2 Qg6, where White avoided changing queens, he somehow succeeded in not only losing the initiative but also messing up the position by letting White's queen penetrate on g7 and soon trap the d6 rook (after a check the king moves to b6, then the queen to e7), at which point Black was forced to resign. :-(
According to engine Rybka, 2..hxg6 (text line) is a better choice. (minus five-something)
And if I had been Black I would have deviated from text line on move #3 by choosing f6-f5. (I did not much like the d6 rook playing the role of a pawn.)

This collapse was a typical example of how much the level of alertness can drop in positions where every move seems to be winning. (I will soon show a game of mine where the same happened to me.)