How is the hadith "If I had known what I know now about my past, I would not have done what I did" reconciled with the prohibition against saying "if"?

Question:
May Allah reward you, Your Eminence, father. This questioner asks about the saying of the Prophet (peace and blessings be upon him) How is it reconciled with what has been reported regarding the prohibition?

Answer:
O brothers, how many times have we answered you? We said: if it is regarding a future matter, there is no harm. But if the "if" is regarding a past matter, then this is not permissible. Also, the Messenger (peace and blessings be upon him) said this regarding good. He did not say it regarding evil, or regarding blaming yourself for missing out on good. There is no harm in blaming yourself for missing out on good. You are not blaming the divine decree; you are blaming yourself. There is no harm. Yes.