The most important part of anything is its beginning. “All beginnings are difficult” (Mekhilta, Yitro), since [at that time,] a person is going from one extreme to the other. But after beginning, and one begins to grow accustomed, then the change is not so difficult.
Accordingly, our spiritual work and awe and fear of Hashem each day all depend on how we began, since each day, we must go back to receive strength from the beginning, when it was most difficult for us. Therefore, we must start anew each time, because it might just be that our beginning was not what it should have been. If so, all of our spiritual work is also lacking perfection, since everything follows after the beginning.
Therefore, we must fortify ourselves and rouse our heart to make a fresh start each time, with a great and fervent enthusiasm and with new determination in our service of Hashem, as if we had not yet started at all, so that our service of Hashem will be what it should be through the force of our new beginning. Similarly, each time, we must entertain this possibility that we has not yet made a proper beginning, and we should determinedly rouse ourselves to make a fresh start from that point on.
Based on Rebbe Nachman, Likutei Moharan I: 62