The acid and base are complementary; one cannot exist without the other.
酸和碱是互补的；没有另一个，一个就无法存在。
Happiness in this world, when it comes, comes incidentally. Make it the objet of pursuit, and it leads us a wild-goose chase, and is never attained. Follow some other object, and very possibly we may find that we have cought happiness without dreaming of it.