I pleaded with Hashem at that time, saying (Deuteronomy 3:23)
Rebbe Nachman teaches that a person must always fortify himself in his prayers-whether he is able to pray with attachment to Hashem and sincere feeling, or whether he is unable to pray with attachment and sincere feeling and his prayers do not come forth fluently from his mouth, G-d forbid. In the second case, he should still fortify himself to pray with all of his might and concentration. This is because at the time that he is able to pray with attachment and sincere feeling and his prayers do come forth fluidly, as they should, then all of his other prayers will ascend on high together with that prayer which he prayed properly.
This is alluded to in the present verse. “I pleaded” – Moshe always pleaded with Hashem. Sometimes he prayed with great d’veikut (attachment to Hashem), and other times, when he could not achieve that d’veikut, he nevertheless prayed with all his might. “At that time, saying” – when the time came that he did merit to pray with d’veikut, that “saying” ascended and carried with it all his other, less acceptable prayers.
Likutei Moharan I: 99