The true meaning of the pain we feel on Tisha b'Av from R. Shimshon Pincus

We are not really lacking.  We have homes, we have children, etc.  But Hashem is lacking, and we are connected to Him.  We feel His pain, so to speak.  His children are scattered throughout the world.  Millions of them are so estranged that they do not even know He is their Father, Such Pain!  On Tisha b'Av we feel the pain of Hakadosh Baruch Hu.

from Gates of Emunah by R. Shimshon Pincus page 19