Why are they deadly?

Is there any cure for them?

How can I know if I am committing them?

Can God forgive me if I have committed them?

"Christians have long focused too much on other people's sins, especially non-Christians. Turning the microscope on ourselves, it becomes all too clear in light of Jesus' perfect example of righteousness and the sheer holiness of God how unrighteous we are by comparison. We like to comfort ourselves with the fact we haven't committed certain "big" sins, like murder, adultery, theft, etc., but what makes the Seven Deadly Sins (which are not directly biblical) perhaps more incisive than the Ten Commandments is their smallness, their personalness. The seven are the quiet, internal roots of so many other sins, and that is why we must explore them—and examine ourselves—so closely." 

Ministrymatters.com