Impatient and uncertain lovers think that they must say or do something kind whenever they meet; they must never be cold.
 Henry David Thoreau, A Week on the Concord and Merrimack Rivers (1849). copy citation

Context

“but it follows after silence, as the buds in the graft do not put forth into leaves till long after the graft has taken. It is a drama in which the parties have no part to act. We are all Mussulmen and fatalists in this respect. Impatient and uncertain lovers think that they must say or do something kind whenever they meet; they must never be cold. But they who are Friends do not do what they think they must, but what they must. Even their Friendship is to some extent but a sublime phenomenon to them. The true and not despairing Friend will address his Friend in some such terms as these.” source