Our Sages said: “If someone comes to kill you, arise to kill him first.” Homiletically, this alludes to the Yetzer Ha-ra (the Evil Inclination) who comes to kill you. So arise in the morning to kill it. For there is no better method for killing one’s Inclination than arising when it is yet night, because once the person began to subdue his Inclination for the sake of serving his Creator, he will get stronger and stronger, with the help of Hashem Who stands watch over him. A line of grace extends over one who studies Torah at night. Another advantage of waking early is that then the person can study Torah with peace of mind and acquire holiness. He can also use that time to pour out prayer and beseech Divine forgiveness — more than can be accomplished in an entire day. All this from arising early!
It is well known that one who does not serve his Creator when he has free time will one day have to give an accounting for even those times that he was not free. Our Sages said that nighttime was created only so that people can study Torah then. One who is accustomed to studying the holy Zohar can see for himself the greatness and the great reward for those who study Torah at night. If, especially, the person arises at midnight — there is no limit to his reward, for he thereby brings great satisfaction to his Creator. One whose lot is among those who dwell the Beis Midrash can easily fulfill this by taking a nap during the day. The Kabbalists write that it is preferable to sleep even six hours during the day if it will guarantee that he can be awake from midnight [and on]. But even other people can train themselves to suffice with minimum sleep. At the very least one should arise like a lion such that he will “wake up” the morning.