Predestination properly understood

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Though the issue at the root of the Reformation was the ultimate authority in the Christian Church, that is, scripture or the office of the pope as the final arbiter of  the content of belief in God and His church (tradition), the heart of the theological conflict was justification and with it predestination. The Protestants denied the value of good works in the matter of salvation, linking our eternity with God after death solely to the will of God.  You were saved or you weren't! The Catholic response at the Council of Trent (1545-1563) is interpreted here by James Hitchcock (2012):

[Trent declared that all people] … stood condemned because of Original Sin and were saved only by the sacrifice of Christ. They had to respond freely to the offer of salvation, but the response was made possible only by “predisposing grace” that was offered to all, without any merit on their part, since God desired that all should be saved. Once accepted, such grace rendered human works meritorious in God’s sight, so that, contrary to the Lutherans, justification was not merely “imputed” to [the individual] by a merciful God, but [all people] were actually made righteous by Christ’s sacrifice.

[Everyone] could overcome sin, because concupiscence, though an ineradicable part of human nature, was merely a disposition to sin, not sin itself. As often as [people] fell, they could be raised up again, especially through the sacrament of penance, because even mortal sin caused the loss only of grace, not of faith.

Although faith was received as a gift, by cooperating with grace and performing good works, believers could grow in hope and charity and be made capable of obeying the Law. But they should also not have ‘vain confidence” that they would never lose the gift of salvation, as the Protestant doctrine of predestination implied, since, because of their free will, [all people] could either grow in righteousness or lose grace through their own fault.

James Hitchcock, 2012, History of the Catholic Church, Ignatius Press, San Francisco