The underlying pain of all Kinos (lamentations) is that there is a terrible feeling of Hashem's absence from our lives. Since the destruction of the Beis HaMikdash (Holy Temple), Hashem has surrounded Himself in secrecy. Hashem desires to be with us in this world. Our hearts are so numb to the point where we don't feel Hashem in our lives. We mourn over the many seforim (books) of the Torah that have been lost.