Might be related to Dark Night of the Soul?

My personal experience is detachment isn't from emotions themselves but reactivity. Not attaching extreme value-laden meaning to stimulus, external or internal. Not taking things personally.

How I experience it in action is through the practice I'm more aware of the first seed of a thought forming and I have the free will to follow it or not. Without awareness they run rampant below the surface until they build up so much pressure they burst through into consciousness as an emotional reaction, positive or negative.

So I can decide if I want to let it go or follow it consciously and introspectively. Ego takes a back seat to awareness. Doesn't mean I'm emotionless or non-reactive, just that I'm more measured, more stable, more true to my real self and they don't linger past the point of usefulness and aren't too extreme.