Critical moments, or, Why do smart players make foolish choices? (Part I)

The words "criticism" and "crisis" share an etymology.  Sometimes we recognize a critical moment in our games.  Having watched reruns of House, we may be able to make a differential diagnosis.  Being human, our reasonable guess may not be right, as we discover in the post-mortem.

I haven't really begun to analyze my games from this weekend's Tim Just's Winter Open XXV, but I think this may be an example:

Charles Swan-Bill Brock

After 16.Qxf3: Black to move

I have to choose how to give my extra piece back.  I played 16...Bxh3, but I now suspect (despite my engine's initial enthusiasm) that it's a mistake to cede the f5 square to the White Nf1.  My guess (which may well be wrong!) is that 16...Qe7 17.dxe6 fxe6, covering my light square weaknesses and creating a second semi-open file for my rooks, would've been stronger.  But either choice is reasonable: even Dr. House's initial diagnosis is usually wrong.

But sometimes the crisis is self-inflicted.  I found it humbling to try to explain my mental lapse a few moves later (my second senseless blunder of the week!)

Charles Swan-Bill Brock

After 18.Kh2: Black to move

I analyzed the piece sacrifice 18...O-O-O 19.Qxf6 Bxf2, hitting both the hanging Re1 and the g1 square.  If one peers deep into the position ;-) , one might notice a refutation.  (I did manage to generate some cheapo potential in the game continuation, but Swan put me away very calmly and efficiently.  His other games, including his loss to Aliyev, were even more impressive.)  

It was a consolation that other strong players could make equally strange oversights.

Bill Brock-Christopher Girardo

After 17.c5: Black to move

Black's choice, 17...Rc8, certainly looks natural.  However....

Dmitry Sergatskov-Bill Brock

White to move after 14...f7-f5

Dmitry's 15.e4 seeks to take advantage of the loose knight on d7.  However....