On Changing the World... / by Cristian Mitreanu

[I]t ought to be remembered that there is nothing more difficult to take in hand, more perilous to conduct, or more uncertain in its success, than to take the lead in the introduction of a new order of things. Because the innovator has for enemies all those who have done well under the old conditions, and lukewarm defenders in those who may do well under the new. This coolness arises partly from fear of the opponents, who have the laws on their side, and partly from the incredulity of men, who do not readily believe in new things until they have had a long experience of them.
— Machiavelli

That's Machiavelli in his famous book "The Prince" (circa 1515). The full text of this English translation by W.K. Marriott is available here.