Just The Simple Meaning

The Rebbe constantly told us to force ourselves to pray with devotion, strongly binding our thoughts to each word. He said that true devotion is listening very carefully to the words you are saying. The Rebbe had told many of his disciples to study the Kabbalistic writings of the Ari. But even these were not advised to follow the Kabbalistic devotions found in these works.

He said that perfect prayer is the plain meaning of such words as Baruch Atah Hashem. Devotion is concentrating on the meaning of the words and listening to them carefully.

(Sichos HaRan #75)