Take long walks in stormy weather or through deep snows in the fields and woods, if you would keep your spirits up. Deal with brute nature. Be cold and hungry and weary. —  Henry David Thoreau  
It is the marriage of the soul with nature that makes the intellect fruitful, and gives birth to imagination. — Henry David Thoreau, American writer (1817-1862)
Only that day dawns to which we are awake. There is more day to dawn. The sun is but a morning star. — Henry David Thoreau, Walden
I can alter my life by altering my attitude. He who would have nothing to do with thorns must never attempt to gather flowers. — Henry David Thoreau
You must live in the present, launch yourself on every wave, find your eternity in each moment. —   Henry David Thoreau
Live each season as it passes; breathe the air, drink the drink, taste the fruit, and resign yourself to the influences of each. — Henry David Thoreau
We must learn to reawaken and keep ourselves awake, not by mechanical aid, but by an infinite expectation of the dawn. —  Henry David Thoreau
Live each season as it passes; breathe the air, drink the drink, taste the fruit, and resign yourself to the influences of each. — Henry David Thoreau
I have a room all to myself; it is nature.

Henry David Thoreau

Journal, 3 January 1853 The Writings of Henry David Thoreau (Boston: Houghton Mifflin, 1906)

I love Nature partly because she is not man, but a retreat from him. None of his institutions control or pervade her. There a different kind of right prevails. In her midst I can be glad with an entire gladness. If this world were all man, I could not stretch myself, I should lose all hope. He is constraint, she is freedom to me. He makes me wish for another world. She makes me content with this.

 The Writings of Henry David Thoreau

(Boston: Houghton Mifflin, 1906) [Journal, 3 January 1853]

Henry David Thoreau  http://www.walden.org/Library/Quotations/Nature