Too often we feel unworthy of God's best because we struggle at times with sin and the flesh. We allow evil voices whisper to us that since we've sinned as a Christian, we've blown it and in order to get back into His grace we must go back to square one. But that is not the truth. To think we have to start over and that we've blown it puts us under law...not grace. Please understand that the very nature of God's grace is that it is abundantly available to be appropriated in this walk when we fail or sin as believers. (See 1 John 1: 9) By God's design we confess our sins to Him and we are forgiven. And yes, grace is not a license to sin. But appropriated it keeps us clean from sin and unrighteousness, no matter what we have done! That's grace.
You are worthy of God's calling on your life. God's call on your life is irrevocable according to the Word. You didn't work to obtain it...and you cannot commit works to cause you to loose it. You are a precious creation of God by His Spirit. Appropriate His grace and mercy in your life. Whatever you've done, simply and honestly confess it to Him. The promise is that you will be forgiven and cleansed! Then keep on keeping on as if it never happened! It's grace and it is yours...in Jesus!