Seneca, Epistle XCIV.64-7
It was not virtue or reason which persuaded Gnaeus Pompeius to take part in foreign and civil warfare; it was his mad craving for unusual glory. Now he attacked Spain and the faction of Sertorius; now he fared forth to enchain the pirates and subdue the seas. These were merely excuses and pretexts for extending his power…. And what impelled Gaius Caesar to the combined ruin of himself and the state? Renown, self-seeking, and the setting no limit to pre-eminence over all other men…. Do you think that Gaius Marius, who was once consul (he received this office on one occasion, and stole it on all the others) courted all his perils by the inspiration of virtue when he was slaughtering the Teutons and the Cimbri, and pursuing Jugurtha through the wilds of Africa? Marius commanded armies, ambition Marius.
When men such as these were disturbing the world, they were themselves disturbed — like cyclones that whirl together what they have seized, but which are first whirled themselves and can for this reason rush on with all the greater force, having no control over themselves; hence, after causing such destruction to others, they feel in their own body the ruinous force which has enabled them to cause havoc to many. You need never believe that a man can become happy through the unhappiness of another.