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Paying unbiased attention to unpleasant feelings and letting them process entirely is like massaging out knots of the mind(r/slatestarcodex)
It doesn’t take any special effort, it’s just mindfulness meditation. Things naturally pop up now and then. When they do you just observe them and they gradually dissipate.
The Science of Enlightenment by Shinzen Young talks about it a lot. For now I’m mainly practicing the method in The Mind Illuminated, supplemented with open focus guided meditation from the Princeton Biofeedback Centre, and both do this pretty effectively for me.