The happiness of your life depends upon the quality of your thoughts: therefore, guard accordingly, and take care that you entertain no notions unsuitable to virtue and reasonable nature.
Happiness depends on ourselves.
Maybe that's why so many people are unhappy; they "entertain notions unsuitable to virtue and reasonable nature".
Isn't it sad that since the First Century, (I think that was Marcus Arelius' time), mankind hasn't improved itself very much in terms of basic human nature?
Mwheel, Yes. Great quotes that transcend time, the nature of man is to take the easiest path and that is good only if the motives are sound.