I have already written some about the role of personal control in feeling happy and satisfied with one's life. But there is another "secret" and it might surprise you.
The role of "expectation". And specific expectations, not larger generalizations. If an experience exceeds your expectation, we tend to feel positive or happy about that experience. Or remember it that way. And if an experience fails to meet our preset expectations, then we tend to feel dissatisfied.
Managing expectations and keeping them more realistic is what the more content among us do. High expectations are hazardous because there is a greater risk of them not being met. The experience would then be evaluated by how the experience failed to meet them than what the actual experience was at the time. A client once told me that he always thought "high goals" would motivate him to achieve more, until he became more aware of the constant and negative "fear of failure" that it produced. The avoidance of negative instead of the pursuit of positive. When he lowered his aim, there was built in "positive reinforcement" for each success and his performance not only increased but he felt much better about it and looked forward to the next challenge. And when he began to coach his employees in this way of thinking, turnover and behavior problems practically disappeared. And production gradually grew.
I will write later about "bias" (personal belief) and how we tend to hold onto expectations created from past experience even when our current experience is different.
Finally, I just watched a TedTalk video featuring the research of Daniel Kahneman. For additional details and another perspective you might find his work interesting.