St Paul warns us that “we shall all stand before the judgment seat of Christ” and “every one of us shall render account to God for himself.” (Rom 14:10,12) Our Lord, before His passion, spoke of the separation of the sheep and the goats in the general judgement at the end of time. We will also each have a personal judgement at the end of our lives, upon which will depend our eternal destiny.
Our Catholic faith teaches us that we are right to trust to the mercy of God. He will save many who would be condemned, if they were submitted to our judgement, for God is infinitely more merciful than we are.
At the same time, Our Lord leaves us in no doubt that some are lost for eternity and so we must not presume upon His mercy, treating His commandments as optional, and taking no care about whether we are in a state of grace.
Famously, Our Lord told us not to judge. He was clearly referring to the divine prerogative of judging the state of soul of a person; this belongs to Him alone. He was not excusing us from the duty to judge our own actions and moral choices, to accept His teaching as true and to reject the false lures of the world.