The only vice that cannot be forgiven is hypocrisy. The repentance of a hypocrite is itself hypocrisy.

Asleep, nobody is a hypocrite

We are not hypocrites in our sleep

He is a hypocrite who professes what he does not believe; not he who does not practice all he wishes or approves

The more faithful preachers are to the Word of God in their preaching, the more liable they are to the charge of hypocrisy. Why? Because the more faithful people are to the Word of God the higher the message is that they will preach. The higher the message, the further they will be from obeying themselves.

Vice leaves, like an ulcer in the flesh, a repentance in the soul which is always scratching itself until it bleeds