Sudden changes

I might be powerful & fast like a river,
but with the force of a landslide you can change my course.
I might be a bird aiming at south guided by instinct,
but you are like a climate change to my natural behaviour.
Intelligible, sudden moves form my future in your hands.
It's smooth like cells communicating inside a body.

I never thought this would happen, but that's how it was inevitably meant to be.