Never do an enemy a small injury.

...people are by nature fickle, and it is easy to persuade them of something, but difficult to keep them persuaded.

I hold it to be of great prudence for men to abstain from threats and insulting words towards any one, for neither the one nor the other in any way diminishes the strength of the enemy; but the one makes him more cautious, and the other increases his hatred of you, and makes him more persevering in his efforts to injure you

One must consider the final result

A prince is also respected when he is a true friend and a true enemy; that is, when he declares himself on the side of one prince against another without any reservation.

A prince being thus obliged to know well how to act as a beast must imitate the fox and the lion, for the lion cannot protect himself from snares, and the fox cannot defend himself from wolves.

Rome remained free for four hundred years and Sparta eight hundred, although their citizens were armed all that time; but many other states that have been disarmed have lost their liberties in less than forty years.