The sixth session of the Council of Trent condemned those claiming an assurance of salvation:
It is not to be said to any one boasting a confidence and certainty of the forgiveness of his sins, that his sins are forgiven, or have been forgiven; seeing this vain confidence, totally remote from piety, may exist in heretics and schismatics. ... As no pious man ought to doubt of the mercy of God, the merit of Christ, and the virtue and efficacy of the sacraments, so every one, while he beholds his own weakness and disinclination, may be in fear and dread respecting his own gracious state; seeing that no man can know with a certainty of faith, as to which there can be no lurking error, that he has obtained the grace of God. (Chapter 9)
Whosoever shall say that he holds it absolutely and infallibly certain that he shall have the great gift of perseverance even unto the end, if he has not learned this by special revelation, let him be anathema. (Canon 16) Such people are
guilty of the sin of presumption. On the other hand, one should hope in his own salvation, provided he has done good works:
Whosoever shall say that the righteous ought not, for the good works which may have been done in God, to expect and hope for eternal recompense from God through his mercy and the merits of Jesus Christ, if he persevere even to the end in well-doing and in keeping the Divine commandments, let him be anathema. (Canon 26)
I once shared 1 John 5:13 with a Roman Catholic priest - These things I have written to you who believe in the name of the Son of God, that you may
know that you have eternal life.. He tried to tell me that the Greek word for "know" in 1 John 5:13 means "uncertain" and you "can't know for sure."