This thread got pretty interesting, especially Cressida and Sol's 'applied Mustachian' observations. I think people don't actually know what they want, and a big part of that is due to being young (not that I'm old enough to know, really).
In reality, lots of young lottery winners / dream job finders end up self-destructing, so neither answer is 100% foolproof. (I'm glad everyone didn't just cheat on the thought experiment and put unrealistic / non-existent extremes forward like paid more than a lottery winning for doing nothing or super-rich but stuck doing that job forever).
So, to make this sound trite, try to also find joy in the journey and making progress to this dream. Don't torture yourself trying to get to some imaginary finish line 'way ahead of schedule', because happiness isn't some exponential curve that keeps going up, it stays high when you hit FI but levels off. From what I can tell, FIRE is a wonderful gift, but you still have lots you still have to do, even if it is just for physical exercise and mental health.
As for me, I hated my first job and would've picked lottery in a heartbeat in my 20's. For the last 8 years, I've had a pretty freakin' good gig. It pays more than I need (as long as I don't go 'consumer sucka', which wouldn't make me happy) and has taken my family to Norway and Dubai for years at a time, all expenses paid (as expats). I don't think I could've even made this dream job up, yet I have it. So why would I want to win the lottery now? To have a pile of money that I didn't work for (and a big target painted on my back)? No thanks! Instead, I can't be appreciative enough to have had a perfect job that got me to FI and allows me to choose when I want to ER.