Our Sages say, “Study is not the main thing, but action” (see Ethics of the Fathers, 1:17). How does one put into practice one’s study of Chassidus?
The Rebbe Rashab once said to Rav Disslin, of blessed memory: “Our sages said, ‘Study is not the main thing, but action.’ In Chassidus, the ‘action’ is prayer at length.”
Shemu’os V’Sipurim, Vol. 1, p. 118.
Explanation: Study of Chassidus alone is “Haskalah”—abstract philosophy. The goal of the Haskalah is Avodah—to refine one’s middos (character traits). Arichus HaTefillah accomplishes this for it involves lengthy meditation on Haskalah with the goal of bringing this awareness to affect and refine one’s emotions, thus imbuing one’s service of Hashem with genuine, deeply-felt inspiration.