Success is not an easy thing to define or measure. So how can you tell when you've "made it" as an author?
By conventional standards, success equals money. People who are known for wealth are considered to be very successful, even elite, and they're admired and envied for all that spare cash. Television shows like Lifestyles of the Rich and Famous and (much newer) Cribs prove that people are fascinated by wealth.
But the truth is, the majority of authors don't make a lot of money. Being an author is often equated with being an artist, and that profession is synonymous with starving. So all the beach houses and big mansions and Bentleys are, sadly, probably well out of your reach.
However, you can make some money with writing. And if you write a lot for lots of different companies, it's even possible to make a living as a writer. If you're living the dream of writing full-time, maybe that means you've made it...even if it feels like you can't always make ends meet financially.
If you have time to write and you're writing something that someone is reading or that someone is paying for and you like what you've written, then you've "made it." Don't measure your success in dollars and cents, because it won't ever add up no matter how much you make. Don't measure your success against someone else, or what anyone in your family says, or even by the statistics you find on blogs like mine. Measure your success by your own standards and ideals. When you dreamed of being an author, you probably weren't dreaming of being awash in riches. You were probably dreaming of being read. Achieve that, and you've achieved great success.