Translated and annotated by Rabbi Aryeh Kaplan, Rabbi Nachman's Wisdom (Breslov Research Institute), page 174.
The Rebbe constantly spoke to us about praying with devotion, telling us to put all our energy into the words of our prayers. Many times he told us to force ourselves to pray. There are so who say that the prayer must come of itself, without being strained. The Rebbe said that they are wrong, and one must do everything in his power to force himself.
Another time the Rebbe spoke of prayer and said that true devotion (kavanah) is the binding of thought to word. If you listen to your own words, then strength will enter your prayers by itself.
All your energy anticipates the time when it will be drawn into words of holiness. When you focus your mind on your prayers, this strength rush to enter the words. Merely concentrate on the words, and strength will enter your prayers without your forcing it.