中文轉英文～！ｔｈｘ～！

幸福: Happiness, well-being, happy....
必然: inevitable, consequential....

You could say,

Happiness is not inevitable(consequential).

or

Being happy is not inevitable(consequential).

or

It is not inevitable(consequential) to be happy.




Hope it helps

幸福不是必然～！
Happiness not necessary ¬! ! !

it is not inevitable to be happy.

Bliss is not a must
Happiness is not a must