In my previous article, I gave a game illustrating the virtues of the Exchange Variation of the Caro-Kann and reasons that I play a line that has a reputation of being harmless. In this game, my opponent gives me an easier time of it playing a different line than the first game, but having no better luck preventing mate. Notice if you will how White is able to transfer pieces to the kingside once the key defensive knight is driven away after 13. dxe5. This is a tactic well worth remembering, as it occurs in many openings. That knight of f6 prevents Qh5 and guards h7, both very important jobs if Black is castled on the kingside.
What exactly did Black do wrong? Here's a list:
1) He allowed his queen bishop to get trapped on d7, when it should have been making the moves Bg4-Bh5-Bg6 to neutralize White's bishop on d3.
2) He exchanged knights on e5, allowing his other knight to be driven away from the defense of his kingside by dxe5.
3) He simply allowed White to win the pawn on h6, opening the h-file with devastating effect. However bad you think a move might be (like Kh8), you can't allow another move which is obviously crushing (Qxh6).
4) He activated White's dormant rook on a1 (which ended up supporting the queen and mating Black) just to grab a few meaningless pawns. You always need to consider if taking a pawn is worth opening a line for your opponent.
5) He basically gave up when he played 23....Bb5, leaving his e-pawn hanging with check. Although, as the old saying goes, "If he had played differently, he would have lost differently", so by that point, it didn't matter too much what he played. Still, you should try to put up the toughest resistance that you can, since your opponent may not see the alternate winning line and let you back in the game, which can be depressing and lead to subsequent inaccurate or desperate moves. In tennis, they say the good players always "make you hit one more ball" even when you are in a dominating position at the net. Despite the extra ball being easy to put away, it provides one more opportunity for the opponent to make a mistake (hit long, wide, or into the net) if he gets too cute or lazy with it. The same applies to chess. Make him make one more move or play one more tactic. He might not see it.
All of these mistakes by Black could come under the heading of "Lack of Precision". He probably gets away with it against players around his rating, but against a stronger player, you have to find another gear and squeeze the maximum out of each move, because that is exactly what he is doing to you!