"Though the ba'al teshuvah may wish to see himself as one reborn and to begin his spiritual life with a sense of wholeness, it is important for him to recognize that even in spiritual rebirth it is not possible to take on everything at once.
The People of Israel, in accepting the Torah, did not receive it all at one time.
Rather, the process was a protracted one, from the early preparatory stage of the seven Noahide laws to the acceptance of additional mitzvot in Egypt, at Marah, and at Sinai, to the full revelation there that followed.
Similarly, a child raised to be an observant Jew takes upon itself the full yoke of the mitzvot only after long preparation: years of training and the gradual, step-by-step assumption of responsibility according to its intellectual readiness and practical capacity.
The essential point is that living beings do not undergo sudden, complete transformations.
The caterpillar does not become a butterfly in a single act but as a result of a gradual process, governed by certain laws.
Within this process there appears to be a series of jumps between distinct stages, and these the ba'al teshuvah also must make from time to time.
But these transitions, too, are neither as quick nor as sharp as they appear.
Sudden entry into the world of Jewish religious life is a rare phenomenon for the simple reason that these changes are highly complex.
The acceptance of Judaism is not a matter of one-time affirmations or moments of revelation.
Such transitory experiences can be important as turning points, but in Judaism they can serve only as the starting point of a very long journey.
It must be remembered that Judaism is a complicated mixture of cultural elements in which belief and practice are closely intertwined.
Without the combination of these elements, Judaism is incomplete.
This is the reason for the prolonged educational process that must be undergone by the Jewish people in its history and by each individual Jew.
It is also why the ba'al teshuvah is likely to find himself engaged for an extended period in such an educational process.
Instead of seeing the intermediate stages as signs of insincerity and ambivalence, as evidence that he is fooling God and himself, he must learn to see them as steps in this process of education."
–Rabbi Adin Steinsaltz
From Teshuvah, p.19, by Rabbi Adin Steinsaltz