Itself is used as the object of a verb or preposition when it refers to something that is the same thing as the subject of the verb.
Scientists have discovered remarkable new evidence showing how the body rebuilds itself while we sleep.
科学家们已经发现了令人瞩目的新证据,证明睡眠时我们的身体如何进行自行恢复。
You use itself to emphasize the thing you are referring to.
I think life itself is a learning process.
我认为生活本身是一个学习的过程。
If you say that someone is, for example, politeness itself or kindness itself, you are emphasizing that they are extremely polite or extremely kind.
He is rarely satisfied with anything less than perfection itself.
他极少对那些自身不完美的事物感到满意。