This passage on managing change comes from Chapter VI of Niccolo Machiavelli’s famous (and infamous) handbook for leaders, The Prince.
“It should be considered that nothing is more difficult to handle, more doubtful of success, nor more dangerous to manage, than to put oneself at the head of introducing a new order of things. For the introducer has all those who benefit from the old order as enemies, and he has lukewarm defenders in all those who might benefit from the new order. The lukewarmness arises partly from fear of adversaries who have the laws on their side and partly from the incredulity of men, who do not truly believe in new things unless they come to have a firm experience of them.”
–Niccolo Machiavelli, The Prince, tr. Harvey C. Mansfield, 2d ed. (Chicago: The University of Chicago Press, 1998), p. 23