The story goes that many years ago the Greeks waged war against the city of Troy. The Greeks besieged the city for 10 years but were unable to penetrate it. Finally they devise a plan to overcome them by trickery. They construct a massive wooden horse and put some of their elite soldiers inside. Then the Greeks made as if they had left, as if they had given up and abandoned the siege. However, they did not, but they hid. They also correctly reasoned that the Trojan people would take the giant wooden horse in to their city as a prize of war, unaware of the danger inside. When night fall had come, the soldiers came out from the inside of the horse and opened the gate for the rest of the hiding army to come in; and thus the Greeks took the city of Troy.
In the same way that Troy was defeated by just letting a wooden horse in, so we can be defeated if we let just a little sin in our lives. Our lives don’t need to be full of sin; just that ‘one thing’ can bring us down.