"We are indeed defined primary by what we do, regardless of whatever we think of ourselves. Like it or not that identity shapes our behaviors, and determines the kind of life we live - from relationships to choices."

I think, the reality is the opposite of this. Of course, i experienced it in my life in my case, so isnt sure, this works in everyone's case.

So, the choices are the origo, the starting point.
Everything depend on our choices. We can do this or do that or do nothing, or do anything. We can react in this way, that way, or not react.
And when we make our decisions, we can shape our behavior, based that choice.
In same case, in same circumstances, more times we can make different choices and decisions, what lead different behavior and lead different results. And if we know, what kind of result is, what we want, moving backward we can realize, what kind of choices need that result. We can modifying our behavior or view or acting, depend that, what we want.

So i think, we aren't that, what we do. Its just the first step on the road to result.
We are our results and its mean, we are our wishes. Accomplished or missed wishes.