Humans have been long dominating the planet and we are the most powerful force on it. The decisions and actions that we make influence not only our species but the whole Earth's ecosystem and beyond. And our decisions and actions are heavily influenced (and one could even say predetermined) by our emotional states. So by improving our emotional well-being we inevitably improve the consequences of our actions thus starting a chain reaction of making things better on a personal as well as collective level.
Changing the circumstances for the better is one way of approaching happiness and that's the usual approach. But there's also a (more) direct approach in which the increased level of happiness is not a byproduct of favorable life's circumstances. This is usually attributed to the field of personal development, involving methods such as meditation, psychotherapy, and various other spiritual/psychological practices, but there's no reason why this couldn't be approached from a scientific/technological perspective.
The dynamics of our mood and emotions are still little understood. The developing science of neurobiology lets us look at the phenomenon of human happiness from a different perspective and raises many important questions, such as - can it be reduced to specific levels of neurotransmitters in the CNS? Is it then like a neurochemical recipe that can be recreated knowing the ingredients and their quantities? What causes spontaneous mood fluctuations, can they be predicted/reshaped?
If we perform better both individually and collectively when in higher emotional states and those bring bigger survival and evolutionary benefits, why emotional fluctuations seem to be not only circumstantially, but also physiologically determined (they also happen spontaneously, without external reasons)? Why some people naturally have more favorable emotional character (more self-confident, social, positive) than others (more prone to sadness, depression, low self-esteem, etc.), is this genetically determined? Can happiness then be bioengineered?
All those and more similar questions are important scientific problems that, if answered, could greatly contribute to creating emotional well-being more quickly and directly. After all - it's not so much that we feel good when we have no problems, but rather that we have no problems when we feel good.