Sung and mai pen rai - the same instruction

No single source. This is mine. The tai chi teacher says: release without collapsing, stay rooted, don't brace against what comes. Pharinee said: it's not that nothing matters, it's that you're not holding onto your reaction to the thing. I spent a long time collecting frameworks for this and I think they were all pointing here. The note I would have written a year ago would have cited six things and drawn a diagram.

This is the diagram: open hands, rooted feet. That's it.