This! The famous Zen Koan of the Master, the Professor, and the overfilled tea cup illustrates this beautifully... I'd highly recommend checking it out! (Overall, the Blue Cliff record is a treasure trove of Koans, for anyone keen on the theme comes highly recommended)

The Zen approach, more than any other, seems to precisely emphasize the purity of 'sit down and shut up'. Shikantaza - literally means 'simply sitting'. It fundamentally involves no staring at walls, no koan to grasp and struggle over, even following your breath is not really a part of it... It really, really is 'just' sitting, in every systemic sense. A practice which has no clear goal or intent, instead focused on removing anything that could act as such, act as any tether over awareness. Awareness untethered, unbounded, past distinction.

Lao Tzu comes to mind... he said it much more succinctly: Wei - Wu Wei (do - not doing). The action of effortlessly being adrift with the flow, the action of surrender of your 'self' and the infinite schemes/designs/narratives that it builds (as someone in the discussion above here aptly suggested). Another quote comes to mind from elsewhere: 'Let go your earthly tether, enter the void, empty and become wind.'