Likutei Moharan 52:4/ליקוטי מוהר"ן נ״ב:ד׳

14. Now you will see something very amazing, how all this is now clearly elucidated in the Mishnah brought above. This is: {Rabbi Chanina the son of Chachinai said: HaNeior Balaylah (He who stays awake at night) and who goes on his way alone and makes room in his heart for batalah (empty thoughts)—he is mitchayev (liable for) his own soul.}

2He who stays awake at night—This follows its simple meaning. In other words, he stays awake at night and secludes himself and speaks at length with His Master.

3and who goes on his way alone—In other words, as explained above, he goes specifically on a secluded road, in a place which people do not frequent. For this is the essence of ideal hitbodedut: at night and specifically on a secluded road, because especially then one can attain the aspect of bitul, as explained above. And this is:

4and makes room in his heart for batalah—In other words, he empties his heart of all the matters of this world—for BaTaLah, in order to merit the aspect of BiTuL. Then he merits having his soul encompassed in necessary reality. And then together with his soul, all the worlds are encompassed in necessary reality, as explained above. And this is:

5he is mitchayev his own soul—The entire world is encompassed together with his soul in the aspect of necessary reality. For through the hitbodedut mentioned above, he merits the aspect of bitul, until his soul becomes encompassed in necessary reality, and through this the entire world becomes encompassed together with his soul in necessary reality. Thus his soul and the entire world are in the aspect of meChuYaV reality, as explained above. And this is the explanation of “he is mitChaYeV his own soul.”