Something you won't know how difficult is until you really do it yourself.想问下这句话有没有错还是这样子对Something you won't know how difficult it is until you really do it yourself.

Something you won't know how difficult is until you really do it yourself.
something 和 it 不能重复，要不然就语法错误了

You won't know how difficult something is until you really do it yourself.
how difficult something is是You won't know的宾语从句。

不对，建议改为：
You will never know how difficult it is until you actually do it yourself.有些事情如果你不亲身实践的话，就不会了解到有多难。

don't is better
sometimes you don't konw how difficult things are until you try to do them youself

都不对.看主杆就知道了.你的两个句子都是：Something until you really do it yourself.很明显不是一个完整的句子.你的意思应当这样来表达：
You will never know how difficult it is until you actually do it yourself.可用will never来加重一下语气.表示如果不亲身实践的话,就不会了解到有多难.如果真要用something,可以在句首加上：For anything,you...“任何事情,除非亲身体验,否则你就不会明白它有多么不易.”

Something you won't know how difficult it is until you really do it yourself.