“Midnight” is called “half and half,” meaning in the middle of the night. “Night” is called “darkness,” and in the middle there is darkness, called “half and half,” half good and half bad, meaning that the light of Kedusha [holiness] shines for him a little bit and he also feels a little bit like he is in the darkness. This is the time for him to mourn the ruin of the Temple in general.
And specifically, man’s heart is called a “house,” as it is written, “Three things broaden one’s mind: a handsome woman, a handsome abode, and handsome Kelim [vessels]” (Berachot 57b). The Zohar interprets, “A handsome woman is his soul; a handsome abode is his heart.” Man’s heart is the house where he lives. It should be a house of Kedusha [holiness], which is to bestow upon the Creator. But this was ruined and in its stead came a structure of self-love.