Likutei Moharan 54:9/ליקוטי מוהר"ן נ״ד:ט׳

19. This corresponds to “During the night I recall my song; I commune with my heart, and my ruach searches” (Psalms 77:7). The night—when the ruach is deposited, corresponding to “Into Your hand I deposit my ruach,” as mentioned above—is the time to collect the good ruach from within the evil ruach. In other words, this is the main time for hitbodedut: secluding oneself with one’s Master and speaking at length with the Holy One; speaking with one’s heart and seeking the good ruach—i.e., the good points one still has, so as to extract them from within the evil ruach, this being the above mentioned aspect of music. Through this the memory is guarded—i.e., through this he merits being mindful that his ultimate purpose is the World to Come, and to continually think about his end, and always attach his thoughts to the World to Come. All this is the aspect of memory, as explained above.

2This is the explanation of “During the night I recall my song; I commune with my heart, and my ruach searches.” If you study this verse carefully, you will find that all its words explain everything that has been mentioned above.

3I recall—This is the aspect of memory, that a person has to always be mindful of the World to Come. This is the aspect of my song—i.e., the aspect of music mentioned above, which is the aspect extracting the good from the evil, as explained above. For by means of the aspect of music and joy a person can remind himself of the World to Come. This is because the memory is guarded by playing music with the hand, which is the aspect of joy, as explained above. And this is:

4During the night—For the main extracting of the good ruach is at night, which is when the ruach is deposited, as explained above. And this is:

5I commune with my heart—By means of the aspect of music and joy, the heart is guarded from the imagination, as explained above. Then a person can pour out his heart like water before God, this being the aspect of “Who has wrapped the waters in a robe?” which was mentioned above; in the aspect of “Pour out your heart like water in the presence of God.” And this is:

6I commune with my heart, and my ruach searches—Through this he is roused to speak with his heart about his eternal purpose, that being the World to Come, and to search and seek to find the good points, the aspect of the good ruach he has within him, in order to return to God through this. For the essence of repentance is subduing the evil ruach and extracting the good ruach, as is known.