On the Happy Life, Section 3 — In Plain English

Seneca — The Senator

For now, I follow nature. This is something all Stoic philosophers agree on: true wisdom means staying close to nature and shaping our behavior according to her laws and example. A happy life is one that fits our own nature. You can't achieve this unless your mind is healthy and stays that way. You also need to be bold and strong, enduring everything with great courage. You must adapt to the times you live in. Care for your body and what it needs, but don't obsess over it. You should appreciate all the good things in life without overvaluing any of them. And you must be able to enjoy Fortune's gifts without becoming her slave.

Seneca — The Senator Original

Meanwhile I follow nature, which is a point upon which every one of the Stoic philosophers are agreed: true wisdom consists in not departing from nature and in moulding our conduct according to her laws and model. A happy life, therefore, is one which is in accordance with its own nature, and cannot be brought about unless in the first place the mind be sound and remain so without interruption, and next, be bold and vigorous, enduring all things with most admirable courage, suited to the times in which it lives, careful of the body and its appurtenances, yet not troublesomely careful. It must also set due value upon all the things which adorn our lives, without over-estimating any one of them, and must be able to enjoy the bounty of Fortune without becoming her slave.