1 John 5:16-17 If anyone sees his brother sinning a sin which does not lead to death, he will ask, and He will give him life for those who commit sin not leading to death. There is sin leading to death. I do not say that he should pray about that. All unrighteousness is sin, and there is sin not leading to death.
There are sins that God can forgive you for and that which lead to death. Matthew 12:31-32 “Therefore I say to you, every sin and blasphemy will be forgiven men, but the blasphemy against the Spirit will not be forgiven men. Anyone who speaks a word against the Son of Man, it will be forgiven him; but whoever speaks against the Holy Spirit, it will not be forgiven him, either in this age or in the age to come.
We have written off people because of what we see them doing. A person can commit a sin and immediately go to God in repentance. King David is one of our perfect example. He had a repentant heart. People were skeptical when they had to receive Paul because of his past life style.
1 Timothy 1:13 even though I used to blaspheme the name of Christ. In my insolence, I persecuted his people. But God had mercy on me because I did it in ignorance and unbelief.