Yet every man in active affairs, who also reads about the past, grows by bitter experience to realize that there are plenty of men, not only among those who mean ill, but among those who mean well, who are ready enough to praise what was done in the past, and yet are incapable of profiting by it when faced by the needs of the present.
 Theodore Roosevelt, Theodore Roosevelt; an Autobiography (1913). copy citation

Context

“The men who have stood highest in our history, as in the history of all countries, are those who scorned injustice, who were incapable of oppressing the weak, or of permitting their country, with their consent, to oppress the weak, but who did not hesitate to draw the sword when to leave it undrawn meant inability to arrest triumphant wrong. All this is so obvious that it ought not to be necessary to repeat it. Yet every man in active affairs, who also reads about the past, grows by bitter experience to realize that there are plenty of men, not only among those who mean ill, but among those who mean well, who are ready enough to praise what was done in the past, and yet are incapable of profiting by it when faced by the needs of the present. During our generation this seems to have been peculiarly the case among the men who have become obsessed with the idea of obtaining universal peace by some cheap patent panacea. There has been a real and substantial growth in the feeling for international responsibility and justice among the great civilized nations during the past threescore or fourscore years.” source