I'm in the same position as you, but I see myself as rather lucky. I worked very hard but I also was taught hard work translates into success, many people don't see that relationship. And I happened to be interested in a lucrative career path.
That's a typical confirmation bias: you worked hard and got successful, so you're tempted to think that it's because you worked hard. Some don't work hard and get successful, many work hard and don't get successful.
The one thing that you clearly can't rule out is luck. Tell people in Gaza that if they work hard they will end up in a situation similar as yours...
all who don't try fail
Obviously, if you don't do, you don't do.
> to use that to question the impact of a human's agency on their own life outcomes
I'm not doing that at all. I am not saying that the effort put into achieving something is worth nothing. What I am saying is that whenever someone is successful, it means that they have been incredibly lucky (and on top of that they worked a lot, maybe). Whenever they compare themselves to someone else who also worked hard but was not successful, the first conclusion to make is that this someone else was not as lucky.
But the first thing that happens when someone gets successful is that they forget how lucky they are, and just start talking about merit. My point is just that whenever you talk about merit, just remember that you were not born in a poor family in a war zone, and that does not make you more deserving.