10,000 iterations.

You have most likely already done 10,000 iterations of something that you can build your career on. If you like doing it and people pay for it, there's nothing like it. Keep compounding.

If you don't like doing it or people don't pay for it, they are simply sunk costs and should be ignored. Find something you like doing and what people pay for. No point in living a life hating what you do or not earning enough.

If it's a new skill you are looking at, understand that it will take 10,000 iterations for you to become really good at it. And if it's important enough for you, you will embrace the challenge.