Part 1. Happiness vs. Success
Am I happy because I am successful or am I successful because I am happy?
Our brain is wired to make sense of our complex surroundings. To do so, it has developed the ability to recognize patterns and develop heuristics, rules of thumb, that help us process and understand the information around us -- e.g. if it is cloudy, we know there is a high chance of rain; or we may choose to eat at a restaurant if it has more cars in the parking lot. This is the brain's 'auto-pilot' mode, and there are good reasons for it; otherwise, we would be in a constant state of alert and acute awareness (everything would be novel!). Yet, the same ability that helps us navigate the world can also lead us astray. For example we tend to infer causality from correlations. Looking at the graph on the right, you may quickly say that more money will make us happier. But if you stop and think, (i.e. get your brain out of the auto-pilot mode), you will reckon that is not necessarily the case. The only thing you can infer is that they move in the same direction.
In Eastern Europe during the winter people tend to sleep more (duh!), but they also eat more imported fruit (oranges) because there is no local fruit on the market. So, both increase in the winter, but it is not that sleeping more makes you eat more oranges, or vice versa. Another factor (winter) is in fact making people sleep more and eat more oranges.
We often think that being successful will make us happier, but researchers have found that happiness does not simply flow from success; instead, happiness can also cause success. In one study involving more than a quarter of a million people, psychologists found that happiness causes success by making people more sociable and altruistic and by improving their ability to resolve conflict through collaboration. Additionally, happy people talk more, which is important in establishing new relationships, and they are more likely to think with originality and flexibility. Experimental evidence also shows that happy people have stronger immune systems, experiencing less pain and perceiving themselves to be healthier.  In the same vein, another study has found that happy workers are "more likely to secure job interviews, to be evaluated more positively by supervisors once they obtain a job, to show superior performance and productivity, and to handle managerial jobs better. They are also less likely to show counter-productive workplace behavior and job burnout."  Further, another study found that people who were happier at age 18 than their peers were more likely to be financially independent and generally doing well in their career.