Success is more like the term "self-efficacy". It directly relates to how a process results in a specific task. Happiness is more of an all encompassing emotion that comes not only from success but from aspects of life that are intangible.
Happiness comes from within a person as a result of actions or feeling that a person experiences. Happiness will provide me with the strength and motivation to be successful. Success will be reflected in my happiness, increasing it.
They are different because success is more goal oriented while happiness is more of an individual feeling. A community can be successful but not happy. An individual can be both successful and happy.