Nothing was ever so unfamiliar and startling to a man as his own thoughts.
To the rarest genius it is the most expensive to succumb and conform to the ways of the world.
 Henry David Thoreau, A Week on the Concord and Merrimack Rivers (1849). copy citation

Context

“It requires to be conciliated by nobler conduct than the world demands or can appreciate. These winged thoughts are like birds, and will not be handled; even hens will not let you touch them like quadrupeds. Nothing was ever so unfamiliar and startling to a man as his own thoughts. To the rarest genius it is the most expensive to succumb and conform to the ways of the world. Genius is the worst of lumber, if the poet would float upon the breeze of popularity. The bird of paradise is obliged constantly to fly against the wind, lest its gay trappings, pressing close to its body, impede its free movements.” source