Niccolò Machiavelli
Discourses on the First Decade of Titus Livius (Chap. 3.9)
That to enjoy constant good Fortune we must change with the Times.

I have repeatedly noted that the good or bad fortune of men depends on whether their methods of acting accord with the character of the times. For we see that in what they do some men act impulsively, others warily and with caution. And because, from inability to preserve the just mean, they in both of these ways overstep the true limit, they commit mistakes in one direction or the other. He, however, will make fewest mistakes, and may expect to prosper most, who, while following the course to which nature inclines him, finds, as I have said, his method of acting in accordance with the times in which he lives.

All know that in his command of the Roman armies, Fabius Maximus displayed a prudence and caution very different from the audacity and hardihood natural to his countrymen; and it was his good fortune that his methods suited with the times. For Hannibal coming into Italy in all the flush of youth and recent success, having already by two defeats stripped Rome of her best soldiers and filled her with dismay, nothing could have been more fortunate for that republic than to find a general able, by his deliberateness and caution, to keep the enemy at bay. Nor, on the other hand, could Fabius have fallen upon times better suited to the methods which he used, and by which he crowned himself with glory. That he acted in accordance with his natural bent, and not from a reasoned choice, we may gather from this, that when Scipio, to bring the war to an end, proposed to pass with his army into Africa, Fabius, unable to depart from his characteristic methods and habits, strenuously opposed him; so that had it rested with him, Hannibal might never have left Italy. For he perceived not that the times had changed, and that with them it was necessary to change the methods of prosecuting the war. Had Fabius, therefore, been King of Rome, he might well have caused the war to end unhappily, not knowing how to accommodate his methods to the change in the times. As it was, he lived in a commonwealth in which there were many citizens, and many different dispositions; and which as it produced a Fabius, excellent at a time when it was necessary to protract hostilities, so also, afterwards gave birth to a Scipio, at a time suited to bring them to a successful close.

And hence it comes that a commonwealth endures longer, and has a more sustained good fortune than a princedom, because from the diversity in the characters of its citizens, it can adapt itself better than a prince can to the diversity of times. For, as I have said before, a man accustomed to follow one method, will never alter it; whence it must needs happen that when times change so as no longer to accord with his method, he will be ruined. Piero Soderini, of whom I have already spoken, was guided in all his actions by patience and gentleness, and he and his country prospered while the times were in harmony with these methods. But, afterwards, when a time came when it behoved him to have done with patience and gentleness, he knew not how to drop them, and was ruined together with his country. Pope Julius II., throughout the whole of his pontificate, was governed by impulse and passion, and because the times were in perfect accord, all his undertakings prospered. But had other times come requiring other qualities, he could not have escaped destruction, since he could not have changed his methods nor his habitual line of conduct.

As to why such changes are impossible, two reasons may be given. One is that we cannot act in opposition to the bent of our nature. The other, that when a man has been very successful while following a particular method, he can never be convinced that it is for his advantage to try some other. And hence it results that a man's fortunes vary, because times change and he does not change with them. So, too, with commonwealths, which, as we have already shown at length, are ruined from not altering their institutions to suit the times. And commonwealths are slower to change than princes are, changes costing them more effort; because occasions must be waited for which shall stir the whole community, and it is not enough that a single citizen alters his method of acting.

But since I have made mention of Fabius Maximus who wore out Hannibal by keeping him at bay, I think it opportune to consider in the following Chapter whether a general who desires to engage his enemy at all risks, can be prevented by that enemy from doing so.