This is a question that you should ask yourself each and every time your opponent makes a move in a chess game. Too often players will overlook this simple question and focus far too much on what he or she is trying to do, not what their opponent is trying to do. Ignoring the strategy that your opponent is trying to implement is similar to going to war and only focusing on your army's goals while ignoring the goals of the enemy.
You are trying to capture your opponent's queen in these next few moves because it appears to be weakly guarded. This can be a good or bad strategy depending on what your opponent is trying to do. If your opponent is attempting to lure you into focusing all of your attention on that poorly guarded queen while setting you up for checkmate, then your attention is focused in the wrong place. Of course you are not a mind reader and do not always know what your opponents strategy is, or if he or she even has a strategy in mind. However, it is critical that you consider what you believe your opponent is trying to do.
When playing chess your goals in the game need to become somewhat secondary to countering the goals that your opponent has. If you see that in two moves you can place your opponent in checkmate, but fail to realize that in one move he or she can capture your attacking pieces, then you have failed to examine what your opponent is trying to do. Once again it is the all-important balance between offense and defense that you are working towards in the game of chess. Focusing all of your attention on one area or the other is a mistake. Find a good balance between the two styles.