Does success make you happy, or does happiness make you successful? This might sound like a pleasant topic to debate over tea and a cucumber sandwich :-) some late Sunday afternoon.
Short answer is that while success probably does make people happy (it’s better than failure for sure), it is also true that having a happy temperament enables you to do the things that turn into success. The “positive affect,” which is the outward sign of happiness, will make it more likely that you’ll land the job, find friends, form a happy marriage or other intimate long-term relationship e.g. make money, be loved in your community, be healthy, etc etc etc.
This really applies only to people in western cultures — and in relatively nonthreatening situations. Maybe “a propensity to experience positive emotions” works well when you have no serious problems anyhow; but when the hurricane or the earthquake shakes you up, a propensity to happiness may be less helpful. Sometimes happy people are judged shallow or complacent. Furthermore, discontent or deep unhappiness can be huge and effective motivators. Some unhappy people are very successful and creative. There are always costs and trade-offs.
Perhaps the most that can be said is: happiness is a great asset, but no guarantee of a perfect life.