That feels like a very unhealthy perspective on life to me (that seems to be quite common in the US).
For example, if you write a book, that can be a major success in itself. The quality of the book has nothing to do with how well it sells.
If your boss is a VC, success is when you exit with an IPO, full stop. The venture doesn't have to be anywhere near profitability if there's enough hype to sell blocks of shares to pension funds.
Unlikely. And that's the point. That's okay. To not get to that level is the norm. There's no sense fearing the obvious, the typical, the usual. Again, worst case you end up where you started (had you done nothing).
It's like traveling isn't it? Eventually you end up back at home (i.e., where you started) and yet you're damn happy you left. So yeah, pull the handle on the slot machine and let the chips fall where they may. No reason to be afraid.
That's ok. That's the point. That's the norm. So if you come up short, so what.