here is a friendly game which i was winning outright yet still managed to lose just as i was expecting my opponent to resign. Just a lesson for us: don't relax yet too early!
mifs adaro(white) -- NN (black)
1.e4 e5 2. Nf3 Nc6 3. Bb5 d6 4.d4 Bd7 5.0-0 Nf6 6.Nc3 ed4 7.Nd4 a6?! 8.Bc6 bc6 9.Re1 Be7 10.f4 0-0 11.h3 c5 12.Nf3 Bc6 13.b3 d5 14.Ne5 Bb7 15.ed5 Nd5 16.Nd5 Bd5 17.c4 Bb7 18. Be3 Bd6 19.Nd3 Qe7 20.Bxc5?? Bxc5+ 21.Kh1 Qd7 22. Nxc5? Qxh3+ 0-1

Yup, he pulled the ole Sneaky Pete pinned pawn attack on ya - LOL! I think we've all been victims of this type thing at one time or another.

Thanks for the post!

This is why visualization is important in chess.

If White saw that Bxc5 Bxc5 was check, then he should have moved Kh1 before taking on c5 (or earlier in the game).

Notice that 20. Bxc5 does uncover the rook attack on Black's queen.