While we're going for definitions, though, let's look at repentance.
Repentance is not "Saying I'm sorry, truly sorry even, for something naughty you did in the past."
Repentance (as I understanding it) is admitting that our past actions have been contrary to the will of God. It "denotes a change of mind, ... a fresh view about God, oneself, and about the world. Repentance means a turning of the heart" (
Bible Dictionary, slightly paraphrased).
When an adult is baptized into the church, he is not required to show evidence of a painstaking remorse over every single past misdeed he may have ever committed. Rather, he is required to show a true desire to follow God according to the new light and understanding received, abandoning all practices and beliefs he now knows to be false. Hence, repentance is not a band-aid to be placed on the wound of a former sin in order to heal it; it is a change in practices to avoid more wounds in the first place. The healing of the wounds comes from the
Atonement, not from repentance.
In other words, when you repent of something (whether it be paying a lesser tithe, smoking, addiction, or incorrect beliefs), you abandon them and recognize that they were contrary, in some fashion, to God's desire. So yes, when a catholic person is baptized, they
do repent of their catholic baptism. They recognize that it was not the baptism that God desired, and as such abandon belief in it as a saving ordinance.
To repent of something doesn't mean to condemn it, or to say that it wasn't a good choice at the time. It just means that you've acknowledged a better way. Repentance is not only for sinners; it is any process by which our desires and beliefs become one with those of God.
At the very least, this is my understanding of repentance, and I like it. It describes repentance as a positive, hope-filled action, and not one of shame and guilt. I believe this understanding is consistent with scriptural usage as well.
So where do I fall in this discussion? I believe that God wants to bless us as much as possible, and he will do so to the measure that we allow him. As we keep his commandments, we are blessed. When we gain greater understanding of his commandments and repent (by acknowledging that the new understanding is more important and abandoning old beliefs and traditions) in order to comply with this new understanding, God will bless us even more. Hence, I believe that God holds many blessings in store for us which are available only as we seek to draw closer to him. It's not that we're condemned or cursed for not being fully compliant. We just cannot receive the additional blessings which God is desirous to give us.