Sichos HaRan 234
Translated by Rabbi Aryeh Kaplan, Rabbi Nachman’s Wisdom (Breslov Research Institute), p. 269
The Rebbe often encouraged people to seclude themselves in meditation and conversation with G-d. He said, “Even if many days and years pass and it seems that you have accomplished nothing with your words, do not abandon it. For every word makes an impression.
“It is written (Job 14:10), ‘Water wears away stone.’ It may seem that water dripping on a stone cannot make any impression. Still, after many years, it can actually make a hole in the stone. We actually see this.
Your heart may be like stone. It may seem that your words of prayer make no impression at all on it. Still, as the days and years pass, your heart of stone will also be penetrated.”