The grace-filled Christian life is supposed to begin in baptism. But those who preserve this grace are rare; the majority of Christians lose it.
We see some people who are more or less depraved in their present lives, because they had poor beginnings which were allowed to develop and take root in them. Others perhaps had good beginnings, but during the early years of their youth, whether by personal inclination or through temptation from others, forgot these beginnings and acquired evil habits. Such people no longer lead a true Christian life.
Our holy faith offers the Mystery of Repentance for this. We have an advocate with the Father, Jesus Christ the righteous (I Jn. 2:1). If you have sinned, acknowledge the sin and repent. God will forgive the sin and once again give you a new heart...and a new spirit (Ez. 36:26).
There is no other way: Either do not sin, or repent. Judging by the number of those who have fallen away from Baptism, one could even say that repentance has become for us the only source of true Christian life.St. Theophan the Recluse (+1894)