What defines us: accepting or rejecting?

"We are defined by what we choose to reject." -Mark Manson, The Subtle Art of Not Giving a F*ck
More broadly stated, rejection of something is a choice--an action. And we are defined by our actions and choices.

If we say "yes" to everything, we end up running around chaotically with no time and no energy and way too much shit to do.

In this quote from Manson, he makes it seem like we default to "yes," and saying "no" is the exception rather than the rule. Instead, it appears to me that maybe we should default to "no" and by so doing, be jealous and protective of our time, our space, and our margin in life.

The line quoted above also doesn't make sense in relation to a previous paragraph of his, which reads:
"The point is this: we all must give a fuck about something in order to value something. And to value something, we must reject that which is not that something. To value X, we must reject non-X."
But then he goes on to say that we are defined by what we choose to reject. Manson characterizes what we choose to reject as non-X, which means that rather, what we choose to reject is itself defined by what we choose to accept. Which is, in this example, X.

Again, more broadly and accurately put, we are defined by our choices, whether that choice is a rejection or an acceptance. And that, I think, is the key.