The Gemorah in Pesochim 66b tells us that when one becomes angry, if he is a wise man, (A CHOCHOM) he loses his wisdom, the proof is from Moshe. And if he is a prophet he loses his prophecy as we see from Elisha, after he bacame angry he called for musicians to make him happy so that the spirit of prophecy would return to him.
This seems difficult to understand. There is no proof that his becoming angry was the cause of losing prophecy. The reason he lost prophecy was because he was no longer happy, and a prophet must be happy, but NOT because he became angry. The proof would seem to be that as soon as he regained his joy, after the musicians played for him, the spirit of prophecy descended on Elisha once more. (It would seem if the cause was getting angry then until the prophet uprooted that character from his sould he would not be worthy of prophecy.)
Tizku Lemitzvos
Yosey
Dear Yosey,
The Gemara in Pesachim 117a does learn from here that prophecy is only possible in happiness. However, our Gemara states that anger stops prophecy because anger must cause a loss of joy. The Gemara is showing what terrible things anger can cause.
As far as "possible anger" being detrimental to his prophecy, I disagree. See Maharsha who says that Moshe got angry 3 times and forgot each time - but not in between! Also, it could be that Elisha wanted to show anger to the king and didn't regret that he lost his prophecy temporarily.
All the best,
Reuven Weiner