Each and every human being instinctively is in pursuit of happiness. Having the best of worldly possessions may temporarily bring one pleasure, but this can never guarantee long term happiness.
Happiness comes from being satisfied with little, and placing ones attention and focus on bigger, non material values. These include the pleasure of Allah and pleasure of fellow human beings.
Happiness comes when we stop thinking about ourselves, when we put Allah and others first. Giving others happiness is a means to achieving the happiness ourselves.
And when we put Allah's pleasure as a focus of our lives, then the very concept of happiness is turned around its head. For a believer who is in pursuant of the pleasure of His Lord, even the outward hardships of this life bring on the bliss in the heart that has been submitted to its Lord.
Happiness is arguably an inner state of being which needs to be cultivated. What triggers happiness in each individual depends on what has been nurtured by the religious spirit. The need to help others to have happiness is an important part of what motivates this contentment in the individual.