What we want versus what we get

No one deliberately plays bad moves at chess. And yet mistakes happen. This is because we play moves we think are good, only to find out, courtesy of our opponent, how bad they really are. Sometimes we might wish a move is good (as in 'I can't see the win but hopefully this move works'), but wishing is not normally an effective strategy.
I believe that a major difference between weak and strong players is that strong players don't make so many wishes. This in part is because they don't need to (because they can see the wins that weaker players can't) but also because they are simply more objective in their choice of moves. If the position requires simple moves, then simple moves it is, and no time wasting looking for more complicated solutions.
So this is why the Giri-Carlsen game from the current Tata Steel tournament was such a big shock. Both Giri and Carlsen chose moves that required a degree of tactical calculation (14. ... cxd5 for Giri, 20.Ng5?? for Carlsen), but it looks like Carlsen's choice was based on a tactical oversight. In the space of 3 moves he had dropped a piece and the game was over.

Carlsen - Giri
Tata Steel Chess 2011 Wijk aan Zee, 17.01.2011

1.d4 Nf6 2.c4 g6 3.g3 Bg7 4.Bg2 d5 5.cxd5 Nxd5 6.Nf3 Nb6 7.Nc3 Nc6 8.e3 0-0 9.0-0 Re8 10.Re1 a5 11.Qd2 e5 12.d5 Nb4 13.e4 c6 14.a3 cxd5 15.axb4 axb4 16.Rxa8 bxc3 17.bxc3 Nxa8 18.exd5 Nb6 19.Rd1 e4 (D)
20.Ng5 e3 21.Qb2 Qxg5 22.Bxe3 Qg4 0-1