When Helen Keller was nineteen months old, a brief illness made her both deaf and blind. With such limitations, how could Keller ever be expected to find happiness?
Because happiness has been considered a personal concept, it is difficult to define（定义）. Many people throughout history have tried. Greek scientist and philosopher Aristotle wrote, "Happiness depends upon ourselves," which is not a definition but an observation that individuals are responsible for their own happiness. Roman statesman and philosopher Lucius Seneca wrote of a particular quality of happiness, saying, "True happiness is to enjoy the present, without anxious dependence upon the future."
Is there a scientific basis（基础）for happiness? Researcher suggests happiness is a matter of perspective: "Truly happy individuals construe life events and daily situations in ways that seem to maintain their happiness, while unhappy individuals construe（理解）experiences in ways that seem to reinforce unhappiness". Basically, this means the way you choose to remember events and situations affects your happiness.
Some research concludes happiness is made up of three parts: pleasure, engagement and meaning. Pleasure involves things that give physical and emotional joy, such as playing a sport or seeing beautiful art. Engagement involves positive interactions（互动）with other people, such as studying or working with people whose company you enjoy. Meaning relates to feeling that your work is useful and important to others.
Even with scientific rationalization（合理化）, questions remain. For example, are younger people happier than older people? In fact, the opposite seems to be true. This may be because younger people tend to experience higher levels of negative emotions, such as anxiety and anger. The young also have less control over their lives because they lack both independence and the ability to make many of their own decisions.
Perhaps the most important question is whether you can change how happy you are. Studies of identical twins suggest that genetics forms about half of your happiness level. Your quality of life influences about 10 percent of your happiness. That means about 40 percent of your happiness is determined by your choices and actions.
From this explanation we can see that one way you can make yourself happier is to set goals. Keller had a definition of happiness in keeping with this idea. She felt happiness did not come from simply trying to satisfy your own desires but rather by contributing your time and skills to improve the world in some way.
Even if you are unable to achieve a goal that makes the world better in some small way, simply trying will likely give your life meaning and, at the same time, happiness.
