The idea of this article is not so much that we become what we believe as that we are those beliefs and thoughts, and yet we can also step out of them, at least for the time being, by being aware of them. Of course, when we are aware of thoughts, we are some other thought in turn, although it is perhaps possible to step out of the realm of thought entirely at least momentarily.
I relate to this so much! As much as we are shaped by our beliefs, we can step out of them, change them, mould ourselves into different (and better versions).