THE sins classified as sins against the Holy Ghost are those of pure malice. They are directly opposed to the love and mercy of God, and on that account, render conversion very difficult. (Source)
1.Presumption of God’s mercy
We continue to sin with the intention of repenting before death comes; or if we make our salvation depend upon our own strength alone and not upon God: or if we rashly expose ourselves to the proximate occasions of sin in the expectation that God will come to our rescue.
There are two kinds of presumption. Either man presumes upon his own capacities, (hoping to be able to save himself without help from on high), or he presumes upon God’s almighty power or his mercy (hoping to obtain his forgiveness without conversion and glory without merit.)
2.Despair
Despair is the willful rejection of hope in that one judges the duties necessary to obtain eternal life impossible to fulfill. Despair is a mortal sin when it arises from distrust of God’s goodness and fidelity.
“By despair, man ceases to hope for his personal salvation from God, for help in attaining it or for the forgiveness of his sins. Despair is contrary to God’s goodness, to his justice – for the Lord is faithful to his promises – and to his mercy.” (more…)