Balance in All Things
The universe tends to unfold as it should. This too shall pass. These sound like clichés, and they are, but they are also profoundly true.
In many places, physics confirm what ancient people already knew about the universe. For example, neither energy or matter may ever be destroyed or created out of nothing. In some cases matter and energy may be converted one from the orher, but the universe's ledger must remain balanced at all times. We can see that sometimes the balancing act may take place across vast distances of both time and space, but it remains true. Opposing forces may sometimes take control, but this is always met with an equal reaction.
Likewise, everything passes. Even the most horrible events in history eventually wound to conclusion. Winter always ends. Spring always returns. Time is cyclical, in both small and large ways. Stay grounded and the wind won't throw you around as badly.