I've done too much. Can God really forgive me?

Yes. He really can. Whatever it is. Saying that doesn't make light of what you've done — it makes a lot of what Jesus did. The cross was not a friendly gesture. It was the cost of taking on the worst of the worst, and your worst is already covered if you'll bring it to him.

Paul, the man who wrote most of the New Testament, was a religious terrorist who organised the murder of Christians. King David committed adultery and arranged a man's death. Peter denied Jesus three times to a servant girl. The Bible's stars are not better than you. They are people Jesus did not give up on. Neither will he give up on you.

Reformed theologians (Calvin, Edwards) and Reformation-era pastoral writers (Bunyan, Luther) wrote at length about what's called 'the freeness of the gospel' — that there is no sin too large for the cross because it was the Son of God who hung there. Augustine, who wrote the Confessions about his own years of immorality, said it bluntly: 'God loves each one of us as if there were only one of us.'

In modern pastoral theology this is sometimes called 'the assurance of pardon.' It's not a feeling, it's a fact: when Jesus said 'It is finished' (John 19:30), he was using a Greek word (tetelestai) stamped on Roman debt receipts. Paid in full.