If you enjoy the effort of doing something more than the result, you will be good at whatever you decide to do.
In my case, when I spend days, weeks, months, or even years writing something, I love that process more than the minutes, hours, or days it takes me to read the result.
I’m not exaggerating to prove a point. It’s true. I love the act of writing more than the result (although the result is really nice icing on the cake that sustains me to the next result). Asking a lot of people if I can write for them is worth the rejection.
That’s how you know you can “win” at something—because you enjoy the mastery time, effort, and rejection required more than the average person.
In my case, I would write for free, I love it so much. Which is precisely how I started writing, for free, on this blog (and still do). Because I love writing so much, I’ve gotten good enough at it that people will pay me to write for them.
Which is a fulfillment of Joker’s absolutism: “If you’re good at something, never do it for free.”
I’ll disagree with him on the “never” aspect, since you sometimes have to work for free to keep learning and growing. But the point is hard work is valued.
So find work you love doing and the value will take care of itself.