The reason there is so much sin among us humans is that we have so many opportunities. We are corrupt in some of our actions and desires, are tempted by the pleasures of this world and its overwhelming presence in our lives, and actively assaulted by spiritual forces of evil.
It seems evident, I believe, that we cannot overcome sin on our own. In fact, trying to perfect ourselves that way can lead us in two directions. Minimizing our sins and becoming self-righteous is one of these paths. Learning the futility of perfecting ourselves on our own on the other hand can lead us to disillusionment with Christianity, anger with God or hedonism depending on our temperaments.
The answer to sin, I believe, is not focusing on it but on Christ’s love for us. Through his grace we can be enabled to love God, our fellow humans, and ourselves. In this state of mind we can see that sin is always harmful to someone and thus find (though not every time) an effective counterbalance to the things that pull us in the direction of sin.