Anyone can hang a piece, but a good blunder requires thought. - Tim Krabbe
The other day I was playing over some of my old OTB games and came across this one from back in 1976. I scored +2 -1 =2 in the tournament, but in my two wins I discovered that both of my opponents resigned in drawn positions. How lucky can you get?
As FM Dennis Monokroussos said, there may be nothing worse than resigning in a winning position; Tim Krabbe once discovered 35 examples where it happened. Monokroussos also added that resigning in a drawn position, as my opponent did in this game, doesn't feel very good either. He wisely added that it isn't always obvious that the position ought to be drawn, so vigilance is needed to the very end.
At Dos Hermanas in 1999 Peter Svidler took a draw against Anand when he had a forced win. And, in his match against Deep Blue in 1997 Kasparov first resigned a game he could have drawn, then later in a tournament took a draw against Joel Lautier in a position that he could have won.