We are all influenced by the external world whether we like it or not. The butterfly effect is an extreme example, but a direct interaction with anything, especially a talking rock, will influence us. Our outputs are a function of our inputs.
That said, being aware of the inputs and their effects on us, and consciously asserting influence over the inputs from within our function body, is incredibly valuable. It touches on mindfulness practices, promoting self awareness and strengthening our independence. While we can’t just flip a switch to be sociopaths fundamentally unaffected by others, we can still practice self awareness, stoicism, and strengthen our resolve as your therapist seems to be advocating for.
For those lacking the kind of awareness promoted by these flavors of mindfulness, the hypnotic effects of the storm are much more enveloping, for better or (more often) worse.