Smile

There's too many options to choose from. 

Health.  If you have it, great and if you don't, it's everpresent (is that a word?).  A good portion of our earthly experience is with this human body.  It houses our spirits and hopefully, lets us do it all, walk, breathe, talk, eat, sleep, laugh,....  But if we don't have good health, temporary or otherwise, how does that effect us?  When I had the flu in October, I felt miserable for 3 days and wanted to die.  Time passes and eventually you feel better.  "But if not..." what would you do?

I'm grateful for good health.  I grateful that I can run, see, hear (partially), talk, use my hands and feel no pain.  We need some illnesses to appreciate our magnificent bodies.