Dissatisfaction is one trait ingrained in humans. Its strange how a man craves for solitude (calling it "some space") when surrounded by people, but seeks company when left alone. Happiness seems to be an alien species on a non-understandable planet called life. Various identification-attempts of the species serve as alibis for various sections of people who tend to explain it differently. Happiness in solitude is often related with an abstract attainment - given the name eternity or divinity by certain sects. Happiness in normal life is mostly identified with the surroundings. A man is "happy" if things and people around him are. The previous sect would reject this perspective as "temporary" or "worldly".
Whichever school of thought you subscribe to, remaining happy is a mammoth task. Whichever excuse you provide yourself as a reason for being happy, on a wider perspective of heart and truth, everything boils down as artificial. A peaceful mind and a contented heart constitute that elusive combination which every man craves for. Only the rarest of mankind actually achieve it.