There are so many things that can make one "happy." Happy is a temporary state of the mind. It only lasts as long as whatever causes that emotion is in effect. Now, nothing wrong with momentary happiness, it is a healthy thing in my opinion.
However, JOY is a spiritual state of being that is eternal. Joy is found in the Lord, and one can have joy even in the most dire of circumstances. While happy is ok, I pray for the joy found in the Lord my God.