Lyric discussion by applejack 

The "it" is just a symbol. It doesn't really mean anything but at the same time it means everything. The song is about how people always think they need something to succeed, and this song is about how people don't need anything ("it") because everyone already has inside of them what they need to succeed.

Therefore, "it" is anything you want it to be. Whether it be money, clarity or whatever...

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