On earth we do not know happiness; we only know bits and pieces of happiness. This explains why those who seek God always find joy, while those who seek joy do not always find God.
Man is lowered to only looking for "quantity joy": chasing down more intense pleasures and emotions, or adding pleasure to pleasure -- just as drug addicts need bigger and bigger doses to get the same level of pleasure.
Only God is happiness--and makes happiness. With him even the joys of the secular life keep their pleasure. I am not only talking about spiritual joys but of all human joy: friendship, health, creativity, art, nature, music. In God is found all of that man thinks the word 'happiness' means and more, since "eye has not seen nor ear heard nor has it entered the heart of man that which God has prepared for those who love him"