There is no one who hasn't backslidden to some degree. Every time we sin we slide back from where we were before we sinned. The term backslidding comes from The Bible.
Hosea 4:16. For Israel slideth back as a backsliding heifer: ...
Jeremiah 3:12. Go and proclaim these words toward the north, and say, Return, thou backsliding Israel, saith the LORD; and I will not cause mine anger to fall upon you: for I am merciful, saith the LORD, and I will not keep anger for ever.
There is great news for one who is backslidden! God wants you back in fellowship with Him again!
Isaiah 55:6. Seek ye the LORD while he may be found, call ye upon him while he is near: Isaish 55:7. Let the wicked forsake his way, and the unrighteous man his thoughts: and let him return unto the LORD, and he will have mercy upon him; and to our God, for he will abundantly pardon.
I John 1:8. If we say that we have no sin, we deceive ourselves, and the truth is not in us. I John 1:9. If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.
Below is a sermon that has helped people restore thier relationship with God. I hope you will read it and be encouraged by it.