Eye contact.
It keeps me on earth, really. One could certainly argue that being tethered is not necessarily a good thing- and, truly, we should hardly strive to be 24/7 occupants of this tangible planet. Drifting off into our own thoughts or exploring the broader spiritual aspects of our experience, are very real and important activities.
But the imperfection of the physical world is no reason to avoid it completely, though we are typically drawn away from it, at least in its fullest form. This becomes clearest in human interaction. The easiest way to detach from our broken human experience is to avoid the fullness of interpersonal communication. This means moving our attention away from the subject or action at hand, breaking our attention into pieces, or fully ignoring others.
The avoidance of eye contact, in particular, allows us to detach from the grounded world, and from the other human beings in it.
When I look someone in the eye as a speak to them, I am trapped in the world, held down to earth by them. I lose the ability to run from my point and drift into my thoughts because they hold me accountable to a sustained interaction. Their eyes become an anchor. While this is a little terrifying, it is also how human beings reach one another. To escape from the world into thoughts and abstractions is also to stand alone, so forming grounded connections first is never a bad idea.
Once we have sustained eye contact and meet one another in the only place where humans meet (earth), we can move on together to explore more complex, less visible, realities without going it alone.
This eye contact, though it initially necessarily grounds us, leads to the unexplainable in a way that is even more fascinating that exploring thoughts on our own. Have you ever had a close conversation, or finished a hug with someone, while looking into their eyes? It tends to render you speechless for a moment. There's a reason so many writers focus so dearly on their subjects' eyes.
It's worth noting that, all worldly grounding and mutual reality exploration aside, the deprivation of eye contact is quite impactful on our regular experience. I knew someone professionally who never looked at me when he spoke, almost always choosing to look at another person or completely away. Such a small thing it is to shift one's eyeball a couple of millimeters, but I could not help but notice. It made me feel alone, abandoned, ignored, even in conversation. There is nothing so lonely as lacking attention from a fellow human even as you interact.
I have heard some refer to eye contact as an art, and it is. Eyes looking at eyes looking at eyes is not a generalizable experience. Each moment of eye contact is unique; each carries with it a meaning besides the mere shared viewing space. By grounding ourselves through one another, we explore thoughts and reality together.