Happiness is considered very important in life. Why is it difficult to define? What factors are important in achieving happiness?
It is no doubt true that the majority of people would like to be happy in their lives. （每个人都想要幸福） While the personal nature（因人而异的特点） of happiness makes it difficult to describe (替换define), there do seem to be some common needs （替换factors）that we all share with regard to experiencing or achieving happiness.（一句话已经引出了全文结构）
Happiness is difficult to define because it means something different to each individual person（personal nature的展开说明）. Nobody can fully understand or experience another person’s feelings, and we all have our own particular passions（特有的激情，同义替换丰富） from which we take pleasure（第一招瞒天过海！这句话还是在展开说明同一个观点，一个意思换个形式说，展示词汇量）. Some people, for example, derive a sense of satisfaction from （derive from搭配地道，满足感源自于）earning money or achieving success, whereas for others（连接）, health and family are much more important (举例加对比论证，常用套路，注意前一句用人做主语，后一句主语切换成对象，体现句式变化). At the same time, a range of other feelings, from excitement to peacefulness, may be associated with the idea of happiness, and the same person may therefore（无痕迹连接表对比和因果） feel happy in a variety of different ways (补充举例扩展后总结观点，句式依然与前文完全不重复，足够多样).
Although it seems almost impossible to give a precise definition of happiness, most people would agree that there are some basic preconditions（高分词汇，替换factors） to achieving it. Firstly, it is hard for a person to be happy if he or she does not have a safe place to live and enough food to eat（否定加假设是常见的强调观点套路，考官的第一个幸福要素是生命基本吃住需求，浅显易懂）. Our basic survival needs（用词准确） must surely be met before we can lead a pleasant life（第二招扭转乾坤！废话展开句，就是把前一句的论证反过来再说一遍，抽象题考官常用套路）. Secondly, the greatest joy in life is usually found in shared experiences with family and friends（第二个要素，和家人朋友的共同经历，不难想到）, and it is rare to find a person who is content to live in complete isolation（又一招扭转乾坤！论证方法依然是反过来再说一遍，纯废话流！逻辑套路类似双否，rare配合isolation负负得正）. Other key factors could be individual freedom and a sense of purpose in life. （最后补充列举两个常识中能想到的打酱油因素，个人自由和人生目标，字数够了就不再展开，单纯展现词汇量）
In conclusion, happiness is difficult to define because it is particular to each individual, but I believe that our basic needs for shelter, food and company（这个company展现功力，是最后总结句的精髓，指代家人朋友的陪伴，万万不可小看，满分词） need to be fulfilled（替换be met，用词太tm多样了） before we can experience it（指代happiness）.