Most of us don't know how to respond to this. And boy, can it be tricky. People often misinterpret their own power of choice because we're not wired to work with the middle term; our default mode is for extremes, and we iterate from there (I know I work that way, I always have and I am honestly glad it works that way for me).
So why do we stress when we're told we can do anything we want? There are two main reasons the way I see it:
1) We don't feel guided or supported with such generic instructions;
2) We don't feel able to live up to the expectation.
I have learned, however, that we frequently underrate our own ability to change something, and rarely trust our gut.
The worst part is starting, because once you do start, you'll spend more time working on it than thinking about why you shouldn't.