By waking up at chatzos (midnight) - even someone who is unable to get up at chatzos exactly- when one strengthens himself to wake up before the light of day appears to engage in Torah and avodah he removes all questions and any atheistic notions (from himself and from the world). He merits complete knowledge and a complete heart, that is like the world which is filled with His glory. He fulfills the pasuk "I have set Hashem always before me." (Tehillim 16:8) By waking before daybreak he merits to daven with tremendous kavanah, for one who wakes at chatzos to engage in Torah is privy to knowledge (da'as) and complete understanding. This is the essence of da'as.
Likutei Halachos, Hilchos Ha'Shkamas Ha'Boker, Halacha 3