When do we make the decision to stop being victimized by the world and take whatever small slice of agency we might have and use it the best we can?

Well, we don't. Most of us don't, anyway. It's hard not to be the victim, because then who do you got to blame? Yourself? Yeah, like who wants that...
It's much easier to just play the victim, it's easier to imagine it's never the right time. For anything. To act. To become who you dream of becoming. Because you might fail and that's a truly horrifying prospect.