In the sefer Igros Uksavim (Vol. 1, p. 25, letter 25), by Rabbi Wolbe, he quotes Rav Moshe Feinstein (בכרך י' סי' קטו בחלק אורח חיים) and says:
There is a response from the great Rabbi Moshe Feinstein, of blessed memory, to someone who struggled with this, where he offers various pieces of advice and concludes his letter by saying, "I conclude that your repentance will be complete, and you will grow in Torah and fear of Heaven."
Does anyone know where to find the original text from the Igros Moshe and what it says?