Essentially, they are 6 manifestations of one and the same sin: rejecting the grace of God to the point of forbidding Him to forgive us and save us
The Gospel says in Matthew, 12, 32:
“And whosoever shall say a word against the Son of man, it shall be forgiven him: but if any man speak against the Holy Ghost, he shall not be forgiven him, neither in this world nor in the future “
The sins against the Holy Spirit consist in the rejection of the grace of God; it is the refusal of salvation, complete rejection of action, unceasing invitations and warnings of the Holy Spirit. They are sins in which the goodness of God is put into question. It is a sin for pure malice, contrary to the goodness which is the Holy Spirit. The will of the person who sins is so hardened that it does not desire the mercy of God and rejects His goodness.
Sin against the Holy Spirit is unforgivable precisely because it is the sinner himself who prevents God from forgiving him . Because God respects the freedom with which He created us, He respects the sinner’s decision to firmly refuse to be forgiven.
The Pope St. Pius X taught in his Large Catechism , which are six sins against the Holy Spirit :
1 – Despair of salvation , when one loses hope in salvation, judging that his life is already lost and that is doomed, even before the Judgment. He thinks divine mercy is small. He does not believe in the power and righteousness of God.