if one loses the sentiments of his heart, he does not know how to seek them again.
 Henry David Thoreau, A Week on the Concord and Merrimack Rivers (1849). copy citation

Context

“We are inclined to lay the chief stress on likeness and not on difference, and in foreign bodies we admit that there are many degrees of warmth below blood heat, but none of cold above it. Mencius says: “If one loses a fowl or a dog, he knows well how to seek them again; if one loses the sentiments of his heart, he does not know how to seek them again. . . . The duties of practical philosophy consist only in seeking after those sentiments of the heart which we have lost; that is all.” One or two persons come to my house from time to time, there being proposed to them the faint possibility of intercourse.” source