1Notice how much of the tightness in you is the verdict you are passing. As the judging comes down, the body tends to come down with it.
This is something you can test rather than something to believe. Catch yourself narrating: he always does this, she has no respect, typical. Then describe the same scene with nothing added, only what actually happened, and see what your shoulders do.
Islamic evidence
Do not grieve over them; do not be distressed by their scheming (Quran 16:127). The instruction is about how much room you hand over to what someone else did.
“So [Prophet] be steadfast: your steadfastness comes only from God. Do not grieve over them; do not be distressed by their scheming”
Qur'an 16:127
Psychological evidence
In an analysis within a trial of mindfulness-based cognitive therapy, the capacity to stand back from your own thinking rose in the people doing that practice and not in those taking medication. That is one specific skill, measured during recovery from depression, and it is not a study of anger or of blame. What it does suggest is that this stepping back is trainable and that it came from doing the practice.
Peter Bieling; Lance L. Hawley; Richard T. Bloch; Kathleen Corcoran; Robert D. Levitan; L. Trevor Young (2012). Journal of Consulting and Clinical Psychology · doi
Review detail
Why it works. Anger is largely built out of the verdict, so easing the verdict takes away its fuel.