To be placid doesn't necessarily mean mediocre.
注释：placid意为宁静、平和、平淡。To be placid代表一种人生态度，个人感觉用PLACID比plain, ordinary等词更能体现这样的意境。
Mediocre意为平庸。加上一个necessarily表示并非一定、必须，更能体现句中“并不等于”的含义。
"to be ordinary people, living a plain and hy life is my greatest wish and hope that it at an early date"
平淡
[词典] dull; flat; insipid; wateriness; uninteresting;
[例句]我们都时不时需要逃避生活中的无聊和平淡。
We all need the occasional escape route from the boring, routine aspects of our lives
Living only in the dull and tasteless is empty and people seem to dull and tasteless. - Chernyshevsky
