One slip can get you the worst of a sharp opening.
A second one can be fatal.
Mackie White
Bergendorff Black
South Africa 1938
Nimzo-Indian Defense, Spielmann Varation E23
1 d4 ♘f6 2 c4 e6 3 ♘c3 ♗b4 4 ♕b3 c5
Black attacks the undefended d-pawn. Now 5 ♘f3 ♘e4! equalizes (6 ♘d2 ♗xc3 7 bxc3 ♘xd2).
5 dxc5 ♘c6 6 ♘f3 ♘e4 7 ♗d2!
White can easily be worse (7 e3? ♗xc3+ 8 bxc3 ♘xc5 9 ♕c2 f5! followed by ...♕a5 and ...♘e4).
7...♘xc5 8 ♕c2 0-0 9 e4?
White recognizes that 9 e3 f5 or 9 a3 ♗xc3 10 ♗xc3 f5 is fairly even.
But 9 e4? allows his better-developed opponent to open up lines.
9...f5
Even better is 9...d5!.
For example, 10 cxd5 exd5 11 exd5 ♖e8+ 12 ♗e2 ♗xc3 13 ♗xc3 ♕xd5. Or 11 ♘xd5 ♗xd2+ 12 ♘xd2 ♘xe4!.
10 exf5 ♖xf5 11 0-0-0 ♕a5 12 a3? ♖xf3!
So that 13 gxf3 ♘d4 wins.
13 axb4 ♘b3+!
Also winning is 13...♕a1+.
14 ♕xb3 ♕a1+ White resigns.
The finale would be 15 ♔c2 ♘d4 mate or 15 ♘b1 ♖xb3.
Georgy Stepanov-Schneiderman White
Peter Romanovsky Black
Leningrad 1926
1 d4 ♘f6 2 c4 e6 3 ♘c3 ♗b4 4 ♕b3 c5 5 ♘f3 ♘e4 6 dxc5 ♘c6 7 ♗d2 ♘xc5 8 ♕c2 f5 9 a3 ♗xc3 10 ♗xc3 0-0 11 b4 ♘e4 12 ♗b2 b6 13 g4 ♘xf2! 14 ♔xf2 fxg4 15 ♖g1 ♕h4+ 16 ♔e3 ♕h6+ 17 ♔d3! gxf3? 18 ♖xg7+ ♕xg7 19 ♗xg7 ♔xg7 20 exf3?? ♖xf3+ 21 ♔e4 d5+! resigns.
Question 132: What happens on 22 cxd5 exd5+ 23 ♔xd5 ?