Bring Me a Musician
When anger caused Elisha's prophecy to leave him, music restored it, teaching that the Shechinah rests only where there is joy.
When the king of Israel came to Elisha in the desert, the prophet was angry at him and said he would not even look at him, were it not for the honor of Yehoshafat king of Yehudah. Then he asked: now bring me a musician. As the musician played, the hand of Hashem came upon him. Chazal explain that because Elisha became angry, his prophecy departed from him, and he needed the music to restore it. From here they teach a principle for every Jew: the Shechinah does not rest on a person amid laziness, sadness, laughter, light-headedness or idle talk, but only amid the joy of a mitzvah. Even a navi of Elisha's stature had to restore his joy before he could hear Hashem's word.
Source: Gemara, Pesachim 117a and 66b (on Melachim II 3:14–15)
Anger and gloom close the heart to holiness, even for a navi. Notice this week what restores your joy when you are upset: a niggun, a walk, a few lines of Tehillim, a call to a cheerful friend. Before you daven or sit down to learn after a frustrating moment, take two minutes for your musician. Hum a niggun quietly, or sing the first line of Lecha Dodi. Let your heart settle, and then begin.