THE Golden Rule; treat others as you would be treated. Pray for the best, plan for the worst. The Finnish concept of Sisu.
Courtesy of the great John Wooden: Talent is God given. Be humble. Fame is man-given. Be grateful. Conceit is self-given. Be careful. Success is never final, failure is never fatal. It's courage that counts. Don't let making a living prevent you from making a life. If you don't have time to do it right, when will you have time to do it over? So many others......
Hopefully irony. That phrase is self-contradictory and really an untenable position. If nothing is true how is the phrase itself meaningful?
I posted that as a joke, it's the "creed" from the Assassin's Creed games. I almost went with But that's over the top nerdy.