Petrarch, On the Remedies of Fortune Good and Bad (2.79):
You don’t have the raw material for perpetuating your tyranny. For indeed, what is a kingdom if not a tyranny grown august with antiquity? That which is bad in its nature cannot become good with time. Add to this the fact that quite often, those who succeed to a throne often step off the well-trod footpath of their ancestors. Examples of this include Hieronymus the Sicilian tyrant and Jugurtha the Numidian, who violated the friendship of the Romans which was cultivated with such faith and so felicitously for a long time by their grandparents. One of them did it with insolence, the other through perfidy, but both of them suffered destruction.
So, you don’t have a successor to your throne? Well then, you will not have an overturner of your acts, but you will still have a population, a lover and cultivator of your name, one that remembers you and owes its liberty to you through the ages. Consider that Fortune has done you a solid favor, because it either took away your son or denied one to you, which is far better even than the fact that it gave you the kingdom in the first place.
Non est tibi materia perpetuande tyrannidis. Nam quid sunt aliud regna quam vetuste tyrannides? Non sit bonum tempore, quod natura est malum. Adde quod persepe qui in regna succedunt, a maiorum suorum calle discedunt. Exemplo sunt Hieronymus Siculus tyrannus, et Iugurtha Numidicus, qui Romanorum amicitiam tanta fide ab avis tamque feliciter diu cultam, cum sua uterque pernicie alter insolentia, alter perfidia, violavit. Non habes igitur successorem regni? Non habebis tuorum actuum eversorem, sed habebis populum, tui nominis amatorem et cultorem, tui memorem, libertatis tibi per secula debitorem. Bene tecum egisse fortunam credito, et melius multo, quod filium tibi vel abstulit vel negavit, quam quod regnum dedit.