"What goes around, comes around." Meaning: they way you treat others will be the way you are treated. I often heard this saying as a child but it was more in response to fighting with my sisters than a broader worldview. I do not think it is limited to relationships but to how we interact with our world: emotionally, geographically, environmentally, etc. Another great illustration of this can be found with the stop-motion animation by Blu called "Big Bang, Big Boom". At about 8 minutes there is a sequence that shows the evolution of man and weapons and it literally comes around.