Two opposite mistakes

The first mistake says anger is always from Shaytan, so if you are angry you have let him in. That takes a normal human state, one that prophets are described as having, and turns it into evidence of a spiritual fault. It adds shame to a situation in which shame is already one of the drivers.

The second mistake goes the other way. It says anger is honesty, that holding it in is fake, and that whatever comes out in the heat of it is the truth finally arriving.

The tradition does not say either of these. It treats anger as a faculty, something that has a proper use and that goes wrong by excess and also by being absent altogether. What is being trained is not the feeling. It is what the feeling is allowed to do.

That is not a modern softening of the tradition to spare your feelings. Ibn Qudamah al-Maqdisi puts it in three grades, in his own book on the censure of anger, in Mukhtasar Minhaj al-Qasidin.

والناس في قوة الغضب على درجات ثلاث: إفراط، وتفريط، واعتدال.

Our rendering: people stand in three degrees with respect to the faculty of anger: excess, deficiency and moderation.

And then, in plain terms, that the deficiency is a defect too.

والتفريط في هذه القوة أيضا مذموم، لأنه يبقى لا حمية له ولا غيرة، ومن فقد الغضب بالكلية، عجز عن رياضة نفسه

Our rendering: and deficiency in this faculty is also blameworthy, because he is left with neither zeal nor protectiveness; and whoever loses anger entirely is unable to train himself.

A man who has never once been angry at anything is not the model in that book. He is the other error.