Why did the period of preparation for receiving the Torah become days of mourning?

This source-based Hagut Yosef essay explores the question: Why did the period of preparation for receiving the Torah become days of mourning? The canonical Hebrew article develops the theme through Torah sources and reflection on human life. This localized discovery layer preserves the source’s meaning and identity and does not add new halakhic, historical, psychological, medical, legal, political, scientific, or empirical claims beyond the Hebrew source.