Yes, justification begins in Baptismal regeneration. It is in holy Baptism that, by the merits of the Passion of Christ, we become new creatures in Him, entirely pure and without stain, washed from every sin, truly born again, and ready to go to heaven if we remain like that. But since we sin daily, and as the Scripture says the just (justified) man falls seven times a day, then rises, God's Mercy instituted the perpetual remedy of the Sacraments, especially of Confession and of Holy Communion, in addition to the aids of prayer and our faith in Christ. If Protestants only understood that justification is lost by grave sin (and almost all Biblical examples amply confirm this - just take the first 3 kings of Israel for e.g. Saul, who was once annointed, and of whom it is written later, that the Spirit of the Lord departed from him; King David, righteous man through and through, except in that one matter of Uriah the Hittite, as God Himself says; and after which he prayed, take not Your Holy Spirit from me, showing the effect of mortal sin; King Solomon, who again explicitly confirms this by falling into a thousand sins after being truly justified - Trent therefore justly pronounces this anathema "If any one shall say, that a man once justified can sin no more, nor lose grace, and that therefore he that falls and sins was never truly justified ... let him be anathema.), then at last would they be able to understand what great gifts the Sacraments are.
The doctrine of rewards and merits is also so clearly taught in Scripture from the very beginning to the very end, and especially by Our Lord Jesus when He says over and over again that He the Son of Man will judge every one by his works, that it seems almost incredible Protestants deny or are unaware of it. Each and every work, as St. Paul says, will be tried in fire, when evil works are found, they must be purged. Only those works that are good and endure will merit, by the grace of God (Gracious Merit, as some Catholic Theologians call it), an eternal reward from the Lord on that day. When Protestants see the Blessed Mother Body and Soul as Queen Crowned in Heaven (Rev 12:1), they fail to understand that this is a Biblical Revelation of the Reward given by God to a perfectly Immaculate Life. And while the other Saints in heaven are not entitled to the same reward, nevertheless they always in the same book are always shown clothed in white, praying to the Lord, and rejoicing in heaven with the holy Angels, each having the reward proper to their own good works.
Rev 14:13
And I heard a voice from heaven, saying to me: Write: Blessed are the dead who die in the Lord. From henceforth now, saith the Spirit, that they may rest from their labours. For their works follow them.And therefore Trent again rejects the false opinion that good works are only signs of justification but not also reasons for its increase. The Lord explains this in the parable of the Vine and the Branches. Those who fail to do good works will be cut off, because they resist the grace of God given to them for that end. Those who correspond to that grace and allow God to do as He wishes will receive more grace. "If any one shall say, that the justice received is not preserved, and also increased in the sight of God through good works; but that the said works are merely the fruits and signs of justification received, but not a cause of the increase thereof; let him be anathema."
"CHAPTER XVI:On the Fruit of Justification, that is, on the Merit of Good Works and on the Manner of that same Merit.
Unto men, therefore, who have been justified after this manner, whether they have preserved uninterruptedly the grace received, or have recovered it when lost, are to be set the words of the Apostle: Abound in every good work, knowing that your labour is not in vain in the Lord;[89] for God is not unrighteous to forget your work, and the love which ye have showed in his name;[90] and, cast not away your confidence, which hath a great recompense.[91] And, for this cause, unto them who work well unto the end,[92] and hoping in God, life eternal is to be proposed, both as a grace mercifully promised to the sons of God through Jesus Christ, and as a recompense which is to be faithfully rendered to their good works and merits according to the promise of God Himself. For this is that crown of righteousness which the Apostle asserted was, after his fight and course, laid up for him, to be given to him by the righteous judge, and not only to him, but unto all that love his coming.[93]"
https://en.wikisource.org/wiki/Canons_and_Decrees_of_the_Council_of_Trent/Session_VI/Justification