The thought of sin can be obsessing. A sin separates you from God. But obsession over sin can also do that. So at some point, the obsession with sin does more harm to your relationship with God than the sin itself. Sometimes the best thing to do for your relationship with God is to call on him and rely on him only. Other times the best thing to do is to pragmatically treat your sin or obsession over sin. Society will tend to reinforce "be pragmatic" and not "trust in God, love God". So you can't rest in pragmatism like society tends to. But pragmatism is a part of life.