If thou workest at that which is before thee  following right reason seriously  vigorously  calmly  without allowing anything else to distract thee  but keeping thy divine part pure  as if thou shouldst be bound to give it back immediately  if thou holdest to this  expecting nothing  fearing nothing  but satisfied with thy present activity according to Nature  and with heroic truth in every word and sound which thou utterest  thou wilt live happy. And there is no man who is able to prevent this.
Marcus Aurelius
happiness