Guilt is experienced because of something one said, thought or did that was wrong and against God's commandments. The Holy Spririt speaks to our spirit telling us we have sinned.
Guilt is experienced as God's way of warning us to repent and turn away from our sins so He can forgive us, cleanse us, and make us entirely guilt free(Psa.51:4). To be guilty means we deserve punishment because we have broken the law. We receive mercy and forgiveness by accepting the salvation and forgiveness offered through the vicarious atonement of our Lord Jesus Christ(1 Tim. 1:13-16).