Grace

How come when we sin and want to be forgiven we do not accept the forgiveness we have been given?

First of all I need to point out if you are saved and have accepted Jesus’s blood as payment for your sins that is your past, present and future sins. Your sins are forgiven and you will enter Heaven. But even after being saved the Bible says all men sin and to restore your relationship with the Father you have to ask for forgiveness for those sins. Now if you are truly his child the Holy Spirit will convict you when you sin. This bringing confession to the Father and any worldly correction needed, example; asking forgiveness from a person you have wronged, paying a debt you owe, etc. “If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.” 1 John 1:9 KJV
The next step is to ask for the Fathers help to move forward without recommitting the sin. This is where Satan works, he keeps throwing the sin in your face telling you it is too bad for God to forgive. As long as he can keep you from accepting Gods grace and keep you out of fellowship with the Father then you are in fellowship with him. Any wedge the Devil can use he will and lies are his specialty. Our fathers voice doesn’t continue to convict you after you have asked for forgiveness, that would be the father of lies voice. We need to learn the difference. The world teaches us we get what we deserve so the grace offered freely by our Heavenly Father is not easy for our worldly minds to accept. We need to study his word and his promises so we are not easily lead astray. “As far as the east is from the west, so far hath he removed our transgressions from us.”
Psalms 103:12 KJV