"It is here in the Garden of Olives where I suffered the most internally, more than in all the rest or my Passion, seeing myself neglected by all, both in Heaven and earth, loaded with the sins of all men. I appeared before the holiness of God, who, without regards to my innocence, hurt me in his furor, making me drink the chalice that contained all the gall and bitterness of his just wrath, as if he had forgotten the name of Father, to sacrifice me to his just anger.
There is no creature that can understand the greatness of the torments I suffered then. It is this same sorrow that the very sinful soul feels, when she appears before the tribunal of divine Holiness, which weighs down upon her, hurts her, oppresses and crushes her in its just rigor. Every night from Thursday to Friday, I will make you participate in this mortal sadness, which I willingly accepted to suffer in the Garden of Olives.
And to accompany me in this humble prayer that I presented then to my Father, you will get up between 11 p.m. and midnight, and prostrate with your face to the ground, as much to appease the divine wrath, requesting mercy for sinners, as to soften in some way the bitterness I was feeling from the abandonment of my apostles, which obliged me to reproach them not to have been able to watch with me for one hour."
(Life and Work II, 72 and 162)
In order to answer the Lord's call "Thus, you did not find the strength to watch for one hour with me", once a month we assure the Holy Hour in union with Christ in Gethsemane.
Therefore, the purpose of the Holy Hour is to unite us to the feelings of the Heart of Jesus, dying in the Garden of Olives, and pray in a spirit of reparation to console the Divine Master.