It's hard being on your own为什么要用being呢

It's hard being on your own = It is hard being on your own
首先指出 It 是形式主语,正式主语是接下去的 being on your own ,
即
Being on your own is hard
being 是动名词引导名词短语 being on your own ,整个短语是主语.
其他类似例句：
Going to school is fun = It's fun going to school
Running the marathon is a challenge = It's a challenge running the marathon