What is the ultimate human happiness?
The ultimate human happiness is closeness to G-d. This is achieved by being similar to, and compatible with, G-d.
Rabbi Samson Raphael Hirsch points out that the Hebrew words simcha (happiness) and tsmicha (growth) are related. Thus, happiness comes as a result of a person growing towards his spiritual potential.
The Baal Shem Tov points out that the letters of the Hebrew word b'simcha (happy) can be rearranged to spell machshava (thought), emphasizing that happiness depends not on your situation, but upon your view of it.