You go out into nature and there is a sensation of forgetting oneself, yet remembering something more fundamental. All the “cheats and tricks” you’ve learnt being amongst people (flirting, appeasing, intimidating, deceiving, negotiating , etc.) don’t work the way they “should” do, and questions like Who? become unimportant. These masks just fall away, and for anyone that identifies strongly with these masks, being in nature can be disconcerting, because you can no longer rely on the rules or script of society.
The ego is a social tool, and relies on society and human relationships for its image and structure, and as a social tool it is quite useful, but it does not reveal the entire picture of who or what you are. It is a narrow beam of light that highlights certain details (the ones we want to show), but leaves others very much out of focus.
Out in nature, a crack appears in the ego, the narrow beam of light dims slightly and lets other details appear, details which you may or may not be familiar with, and which you may or may not find agreeable. In society we may come to believe that we are an ego that wears a body, but in nature this becomes reversed and we have space to realise we are a body that carries an ego.
I feel the same doing aikido too. When practicing a technique, I am in physical contact with another person, and cannot rely on my social image to interact with them. In this way I come face-to-face with my own physical limitations, which I cannot overcome by presenting a new image to them, but only by confronting the existence of my body.
The body is our organic contact with reality, and the ego is a social tool. Perhaps we’ve spent more of our lives living in a social mode than the organic, and it’s difficult to change that habit. But the more we spend time with nature, the more the organic reality asserts itself and the social reality is put into perspective.