Proverbs 18:21 - "Death and life are in the power of the tongue..."
Job constantly feared that God would punish him and his family because he kept thinking that his sons and sinned against God. He would get up early in the morning to offer burnt sacrifices, saying, "It may be that my sons have sinned and cursed God in their hearts."
So Job kept confessing the sins of his sons and greatly fearing that something terrible would happen to him and his family (Job 3:25). Job's sin-consciousness opened the door to Satan. His preoccupation with sins that his family may have committed gave Satan the opportunity to bring death and destruction into his life. God had a hedge of protection around Job. But when he started being sin-conscious and having a fearful expectation of judgment, the hedge was removed and Satan could attack him(Job 1:9-12).
If you have sinned don't say, "I have failed again. I deserve to be punished by God." Know that you already have forgiveness of sins because Jesus was punished and condemned in your place! (Ephesians 1:7). So say, "I am the righteousness of God in Christ. Jesus, you are my holiness and perfection" (1 Corinthians 1:30; 2 Corinthians 5:21).
Such believing and confessing not only pleases God, but also shuts the door on Satan so that he cannot make any inroad into your life.