Agressive defense is good, if you can achieve it. Simplifying is good, if you can achieve it. But what do you do where neither of these methods is possible? In that case you must bide your time, not with passive squirming, but by constantly remaining in the lookout for agressive counterplay and useful simplification.
How the defender can work towards these goals is shown in the following play: Black is two pawns ahead with a solid position. But when White hits out boldly, Black cannot depend on his material advantage alone.
Many players in Black's position would be unprepared for the vicious attack now unleashed by White. Of course, White gets nowhere with 1.Bxf6 (hoping for 1...Bxf6?? 2.Qxh7 Mate). Black replies 1.Rxc2! with nothing to fear. But White has a different way:
(Notes by American Grandmaster Al Horowitz)