Did you know that guilt can be good? Guilt means that your conscience is working. The time to be concerned is when you don't feel guilt, when you can sin against God again and again and feel no remorse or sense of wrongdoing. Hebrews 12:6 says, "The Lord discipline those he loves, and he punishes each one he accepts as his child." If you are a believer—one of His sons or daughters—and you go astray, the Holy Spirit will convict you of your sin. He will call you on it, because He loves you. He will reprove you, just like a father reproves his child.
God disciplines His own children. So if you can do things that you know are wrong and don't feel remorse about it, then I have to wonder whether you are a child of God. But if you feel busted and come under the conviction of the Holy Spirit the moment you cross the line, then that is good. The Holy Spirit is working.
But we also need to know the difference between the Holy Spirit's conviction and the devil's accusations. The devil always will try to keep you from the cross, while the Holy Spirit always will bring you to it. When you know you have sinned, the devil says, "Run! Don't go to God!" He will try to drive you away into despair.
But the Holy Spirit says, "Repent—now." So that is what you need to do. Ask for God's forgiveness. And once you have, don't keep going over and over it again. You should not choose to remember what God has chosen to forget. God has a big eraser. And if He has used it your life, then be thankful that your sin is not only forgiven, but it is forgotten.