“When a person has an awareness of G-d, it is as if he has rebuilt the Temple in his day” (B’rakhot 33a)
This is what is meant by building our personal Beit HaMikdash (Temple), which is a pure, holy, and simple emuna (faith in Hashem) and a deep recognition of Hashem. “”‘Understanding’ means the recognition of the Creator” (Bamidbar Rabba 10:1). Through our Torah study, with each word we utter in prayer to Hashem, with our every good deed, and by overcoming our evil inclination, we each build this inner Temple.
Based on In All Our Ways, Collected Discourses of Rabbi Yaakov Meir Schechter