Rabbi Moshe Ben-Chaim
Reader: You always say that the Torah does not hold of luck or superstition. If so, then one thing confuses me. Those whose parents are still alive leave shul during Yizkor. What is the reason for this if not superstition? Also--on a side note of superstition, why are people so paranoid about their fingernails after they are cut? Some people burn them, some flush them, and I've heard that if a pregnant woman steps on one, she'll miscarry. Where do these ideas come from? Thanks
Mesora: There are no such thing as powers outside of God. You must understand this clearly. Then all else will not pose questions to you, as you will be secure in the rational proof that as only God is the source of all creation, God alone can change the nature of events and properties of objects. This must be clear in your mind.
Once it is, when you come across strange statements in the Torah, you will strive to give rational explanations not assuming powers outside of God.
Regarding your specific questions, leaving shul is not because we feel by staying we die or become mourners. A mourner does not shave or manicure. Perhaps fingernails cause another person psychological anxiety, as he associates to death.
Fear of death can cause miscarriages, fingernails cannot.