What is the relationship between the Self and Nature in Walden Pond by Thoreau ?

In Thoreau's account of his time at Walden Pond, he insists that it is only in Nature that a person can really find himself. The pressures of society life impose too much responsibility and frivolity onto a person, so retreating into Nature allows for a person to free his mind and his soul long enough to discover what is essential.

Live in each season as it passes; breathe the air, drink the drink, taste the fruit, and resign yourself to the influence of the earth.

Here, Thoreau insists that one must connect to the earth and allow one's self to be influenced by this connection. It is only in doing so that we learn to live in harmony with the circumstances of our lives and grow able to overcome the changes that happen around us at all times.

I went to the woods because I wished to live deliberately, to front only the essential facts of life, and see if I could not learn what it had to teach, and not, when I came to die, discover that I had not lived.

And here, in these famous lines from Walden, Thoreau is saying that it is only in Nature, removed from society, that he believed he could truly live. Being in Nature forced him to confront what his real requirements were for living, and this minimalism allowed him to explore himself more fully.