John Piper writes: 

“God has put eternity in man’s mind and filled the human heart with longing.  But we know not what we long for until we see the breathtaking God.  This is the cause of universal restlessness…The world has an inconsolable longing.  It tries to satisfy the longing with scenic vacations, accomplishments of creativity, stunning cinematic productions, sexual exploits, sports extravaganzas, hallucinogenic drugs, ascetic rigors, managerial excellence, etc.  But the longing remains.”