It is the duty of every person to act in accord with nature with regard to guarding his health and gaining a livelihood. However, we have seen with our own eyes that there are many people who lived in accord with nature, and they were very careful about their health and put in great and energetic effort towards earning their livelihood, and yet, for all their effort, they came up with nothing. Instead, what one is obligated to believe and remember is what the Torah says: You shall remember Hashem, your God, that it is He Who gives you strength to make wealth (Devarim 8:18). Everything that occurs to a person through nature, for better or worse, is all by decree of God, in accord with the person’s deeds; except that if the person went out of line and harmed himself by doing something that is naturally harmful, he will be punished for that—despite the fact the harm was in any event decreed upon him—and he will be held accountable for behaving improperly.
י׳ במרחשון ה׳תשפ״א
My brother and my nation, take this Torah book, in this and like this learn well, listen and revival your soul, you will achieve joy and joy, in this world and next world. (from introduction of the author) 1