"It is a sin against the Holy Spirit"
How do you sin against the Holy Spirit?
There is only one way, that is by consciously refusing to accept God's forgiveness. God does not forgive because someone refuses to accept His forgiveness. You cannot do that by accident. It takes a conscious and continuous effort on your part.
"The correct interpretation, as it is given to us by the Church Fathers, is this: blasphemy against the Holy Spirit is the denial by man out of hatred of God's power to save him. Even more simply, the man who does not believe that the grace of God--the Father, the Son, and the Holy Spirit--can save him, closes his heart to the actions of the Holy Spirit; he does not accept Grace. He does not proceed to repentance. He fights against the sanctifying and saving act of God. He creates within himself a sorrowful and incurable condition."
