Being thankful for whatever life throws at you leads to happiness.
You are bound to have ups and downs in life. Every human being goes through that cycle. This happens to the richest person in the world and the wisest and the most noble. No one is spared of this cycle.
However, at the end of the day it does not matter what life throws at you, but how you handle it and respond to it. Above all, how you embrace it gratefully, and do all in your power to turn your minuses into pluses.