Meditations, Book 10, Section 2

Marcus Aurelius — The Emperor

Since you are completely governed by nature, pay attention to what your nature generally requires. Once you do that, check if your nature as a living being would be harmed by it. If not, go ahead. Next, examine what your nature as a living being requires. Whatever that is, you can accept it and do it — as long as your nature as a reasonable being won't be harmed. And whatever is reasonable is also social. Stick to these rules. Don't worry about pointless things.

Marcus Aurelius — The Emperor Original

As one who is altogether governed by nature, let it be thy care to observe what it is that thy nature in general doth require. That done, if thou find not that thy nature, as thou art a living sensible creature, will be the worse for it, thou mayest proceed. Next then thou must examine, what thy nature as thou art a living sensible creature, doth require. And that, whatsoever it be, thou mayest admit of and do it, if thy nature as thou art a reasonable living creature, will not be the worse for it. Now whatsoever is reasonable, is also sociable, Keep thyself to these rules, and trouble not thyself about idle things.