Groundless Ground & Not
Meditation/spiritual teachers often talk about the importance of no attachment, of allowing experiences come and go as guests, and so on.
What they sometimes leave out is that this either comes on its own, effortlessly, or don't.
When we are not familiar with the groundless ground - the unchangeable context for the changing content of our experiences, the formless and choiceless awareness - then any attempts of no attachment is difficult at best, and often impossible. We are exclusively in the realm of attachment, and any attempts of no attachment is just another expression of attachment.
When we become more familiar with this groundless ground, then this no attachment comes as a natural and effortless result of this groundless ground, which is timeless and free from any stickiness. For a while, it is there sometimes more in the background and other times more in the foreground, often amplified through sitting practice (such as shikantaza). Then at some point, it may 'pop' and have a stable presence. Now, experiences come and go on their own, and they have nowhere to stick.
Sensations, feelings, emotions, thoughts - all of these now come and go as guests, with nowhere to stick. The mind is revealed as a mirror faithfully reflecting anything coming up in the present, and the content leaves no traces.
We now see how we create such a drama for ourselves whenever there is struggle with the content of experiences, when we try to hold onto some and push other away. And we see how this is inevitable when the presence of the groundless ground is not stable.
We also see how all this struggle and drama falls away when the groundless ground is stably present and the content has nowhere to stick. (And we see how any attachment is to the content of our experiences - to a sensation, feeling, emotion, thought - and not to any "external" object.)
Of course, this groundless ground is always present. It is that which allows the content to come and go, as it naturally does on its own (in our experiences, and in existence as a whole). The difference is how familiar it is in our awareness, how present it is in awareness.
And to familiarize ourselves with this groundless ground, we can engage in various forms of practice such as sitting meditation or different forms of inquiry (headlessness, byron katie, atma vichara etc.).