Accordingly, the happy life is the one that is in harmony with its own nature, and the only way it can be achieved is if, first, the mind is sound and constantly in possession of its sanity, and secondly, if it is brave and vigorous, and, in addition, capable of the noblest endurance, adapting to every new situation, attentive to the body and to all that affects it, but not in an anxious way, and finally, if it concerns itself with all the things that enhance life, without showing indie respect for any one of them, taking advantage of Fortune’s gifts, but not becoming their slave.

Seneca, ‘On the Happy Life’