If you imagine it, you can become it.

If you can imagine it, you can become it.

If you can dream it, you can do it.
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I have seen those kinds of sentences a lot and I was wondering what the it refers to? I have known that it usually refers to something mentioned before but in the sentences, I can't not see what it is so then I should check the whole part to see what it refers to or idiomatically it is used and I can put any words into the it, like

If you can imagine a teacher, you can become it.
If you can dream a teacher, you can do it.

What do you native English speakers think? Thank you so much as usual in advance.