When we fail, we must run to God. When we are with God, we must know our failure is not final

7 Nathan said to David, “You are the man! Thus says the Lord, the God of Israel, ‘I anointed you king over Israel, and I delivered you out of the hand of Saul. 8 And I gave you your master’s house and your master’s wives into your arms and gave you the house of Israel and of Judah. And if this were too little, I would add to you as much more.9 Why have you despised the word of the Lord, to do what is evil in his sight? You have struck down Uriah the Hittite with the sword and have taken his wife to be your wife and have killed him with the sword of the Ammonites.10 Now therefore the sword shall never depart from your house, because you have despised me and have taken the wife of Uriah the Hittite to be your wife.’11 Thus says the Lord, ‘Behold, I will raise up evil against you out of your own house. And I will take your wives before your eyes and give them to your neighbor, and he shall lie with your wives in the sight of this sun.12 For you did it secretly, but I will do this thing before all Israel and before the sun.’ ”
2 Samuel 12:7-12

When we fail. We genuinely repent. And God forgives us.

David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die.
2 Samuel 12:13

14 Nevertheless, because by this deed you have utterly scorned the Lord, the child who is born to you shall die.” 15 Then Nathan went to his house. And the Lord afflicted the child that Uriah’s wife bore to David, and he became sick.
2 Samuel 12:14-15

God wants to forgive you, not harm you.

16 David therefore sought God on behalf of the child. And David fasted and went in and lay all night on the ground.17 And the elders of his house stood beside him, to raise him from the ground, but he would not, nor did he eat food with them.18 On the seventh day the child died. And the servants of David were afraid to tell him that the child was dead, for they said, “Behold, while the child was yet alive, we spoke to him, and he did not listen to us. How then can we say to him the child is dead? He may do himself some harm.”19 But when David saw that his servants were whispering together, David understood that the child was dead. And David said to his servants, “Is the child dead?” They said, “He is dead.”20 Then David arose from the earth and washed and anointed himself and changed his clothes. And he went into the house of the Lord and worshiped. He then went to his own house. And when he asked, they set food before him, and he ate.21 Then his servants said to him, “What is this thing that you have done? You fasted and wept for the child while he was alive; but when the child died, you arose and ate food.”22 He said, “While the child was still alive, I fasted and wept, for I said, ‘Who knows whether the Lord will be gracious to me, that the child may live?’ 23 But now he is dead. Why should I fast? Can I bring him back again? I shall go to him, but he will not return to me.” 
2 Samuel 12:16-23

We are forgiven, we should worship.

24 Then David comforted his wife, Bathsheba, and went in to her and lay with her, and she bore a son, and he called his name Solomon. And the Lord loved him 25 and sent a message by Nathan the prophet. So he called his name Jedidiah, because of the Lord. 
2 Samuel 12:24-25