ChessTempo has defensive tactics missed with attacking tactics in its 'mixed mode'. They won't tell you what's in the position, so you'll have to figure it out by yourself.
During your game, a good rule of thumb is simply to ask yourself "what does my opponent want to do ?" after he has played.
I figured out today that perhaps my biggest chess problem is overlooking my opponent's tactical opportunities on my half of the board. I see my tactics against my opponent perfectly well. It's just when I am defending and my opponent has tactical opportunities, I frequently miss them.
I have heard the advice before to solve tactical problems from the other side (the defending side) of the board as a way to solve this. Is there any chess tactics interface that allows the player to do this, or any chess tactics interface centered around defensive tactics or spotting the opponent's tactics? I lose so many games like this that I think I would be at least 50 rating points better if I could iron this out a bit.