We are declared "not guilty" because of Christ. It's in the Bible, Romans 3:21-22, TLB. "But now God has shown us a different way to heaven—not by ‘being good enough' and trying to keep His laws, but by a new way (though not new, really, for the Scriptures told about it long ago). Now God says He will accept and acquit us—declare us ‘not guilty'—if we trust Jesus Christ to take away our sins. And we all can be saved in this same way, by coming to Christ, no matter who we are or what we have been like."
Christ can relieve our guilty conscience. It's in the Bible, I John 3:19-20, NIV. "This then is how we know that we belong to the truth, and how we set our hearts at rest in His presence whenever our hearts condemn us. For God is greater than our hearts, and He knows everything."
What should I remember if I am feeling guilty? It's in the Bible, Romans 8:31-39, TLB. "What can we ever say to such wonderful things as these? If God is on our side, who can ever be against us? Since He did not spare even His own Son for us but gave Him up for us all, won't He also surely give us everything else? Who dares accuse us whom God has chosen for His own? Will God? No! He is the one who has forgiven us and given us right standing with himself. Who then will condemn us? Will Christ? No! For He is the one who died for us and came back to life again for us and is sitting at the place of highest honor next to God, pleading for us there in heaven.
Believe that God has indeed forgiven you and quit feeling guilty. It's in the Bible, Psalm 32:1-6, TLB. "What happiness for those whose guilt has been forgiven! What joys when sins are covered over! What relief for those who have confessed their sins and God has cleared their record. There was a time when I wouldn't admit what a sinner I was. But my dishonesty made me miserable and filled my days with frustration. All day and all night Your hand was heavy on me. My strength evaporated like water on a sunny day until I finally admitted all my sins to You and stopped trying to hide them. I said to myself, ‘I will confess them to the Lord.' And You forgave me! All my guilt is gone. Now I say that each believer should confess his sins to God when he is aware of them, while there is time to be forgiven. Judgment will not touch him if he does. You are my hiding place from every storm of life; You even keep me from getting into trouble! You surround me with songs of victory."