If you become part of Christ’s Body (through Baptism), the Holy Spirit gives you many of Christ’s spiritual gifts (through Confirmation), and Christ feeds you Himself (through Communion), you are obviously going to become more and more like Christ, both in soul and body.
Like John said in his letter, “You are children of God now. What you will become has not yet been revealed.”
So yes, God gives us many graces suddenly. But since He doesn’t do anything to us against our wills, and since we have a lot of bad habits and concupiscence to get over, even when we are willing (as St. Paul complained of himself, when he talked about what he couldn’t do), we are also given many graces slowly – or at least, we are only able to make use of them slowly!
This is why St. Paul and all the early Christians, especially monks, were fond of comparing the Christian life to being an athlete in training. (The Greek for athletic training was “askesis”, so asceticism is being in training.) Whenever you faced temptation or persecution, and whenever you died or were martyred, that was an athletic event you were trying to win. God was the coach, and the angels and saints were the crowd of fans cheering you on.
If you didn’t die, then (whether you “lost” or “won” your race or wrestling match), you would train more, and then face more athletic events in the future. Hopefully you got better and better. If you didn’t, you just dug in and kept training. The results were up to God’s grace; the effort to try and fail and try again was the individual’s trusting response to Him.
If you keep trying again until you die, you win the prize! If at the end you decide you’d rather go to Hell… God will let you, and all that training will go to waste. So some parts of grace are sudden, some take time to unfold. But God will not force any gifts upon you.
As the Christian life progressed and your soul became more Christlike, there was every possibility that your body would also be filled with Christ’s grace. On the small scale, one would become less tempted by certain sins one had been training against, or one would learn to deal with temptation and go on. Some people, like the apostles, would have their bodies become so Christlike that Christ worked miracles through them, or even through things like handkerchiefs and their shadows.
So basically, justification is all about staying on the Vine and growing in Him. If you abide in Him, He will abide in you – more and more, every day.