Well, certainly not being baptized into "Sin". ;O)
Baptism is not what saves you. Your faith in God is what saves you. That being said there are certain things that illustrate this faith in God (repentance of sin for example). But all of this comes about because of a changed heart.
Baptism is not what saves you. Your faith in God is what saves you
Only God saves you. Baptism is a petition for adoption. We trust that those who are baptized can be saved because God hears our prayers. God does not compel. We also know that men can reject God and be lost, through ingratitude, even if they are baptized.
You, being Reformed, can never say that it is you who believes, but God who makes you believe.
You may have a point about the heart. Some of us on this thread have been discussing Gregory Palamas who defended those who prayed the prayer of the heart, "Lord Jesus Christ, Son of God, have mercy on me (a sinner)." They repeated the prayer and concentrated the mind in the heart while doing so. They claimed to see the light of Christ which entered their hearts and their hearts were indeed changed--saved or deified.
The purification of the heart seems to be a widely held belief in Christianity.