There's a lot of books published a year. Like a lot. In 2016 Amazon Createspace published over half-a-million unique books (not counting the various copies of said books sold). Total different self-published books overall? Over 800,000. And with funding for libraries on the decline, bookstores disappearing, and a measly 15% or so of the total population picking up a book and reading it throughout the year, you'd think the economics of supply and demand would have kicked in. On wait, they have. The few people that still do read are buying less books and reading for less time in the day. Avid readers now only read for an average of fifteen minutes a day. And although audiobooks have picked up in popularity, going from 11% of readership population to 18%, stealing many physical book readers away, the facts are obvious: we are slowly turning into a society that no longer reads. Perhaps its because many people are used to quick, vibrant, on-the-spot entertainment, free and easy to access (usually through our phones or other media devices). Perhaps too many people are getting caught up in the modern day and fighting financial burdens to have time to read. If you are one of the few who still actively and voraciously read, you are part of a community which might be shrinking by the day. So as an author, those facts might be daunting, especially when one's work can be drowned within a sea of other books in a matter of milliseconds.
I myself have no idea of the scope in which my books will reach. Yes, they've been bought in many countries, in many states, and by many people of varying class and race. But there are plenty of times where I get no sales. 0. Nada. It's the name of the game. The nature of the beast. So you either put your shoes back on and walk out of the office or you keep grinding away.
But why? If you don't reach success, why bother? Because I measure my success based on the personal satisfaction I get from finishing a quality book and putting it out there. Now yes, I market like crazy, have a mailing list, have an online presence, communicate with my fans, and attend writing events, which all help make me as an individual more marketable, but in the end, I have no frikin clue if I'll be financially successful, or sell even one copy, ten, or a hundred. I do it, cause I want to. Cause if I don't, I'm failing my dreams and ambitions. Money can be earned in a variety of ways, but satisfaction from doing something that you love, man, that's limited.
So if you're an author, a musician, a baker, or whatever else have you, separate worldly success from the personal satisfaction. If money and fame follow, sweet. If not, well at least you got a kick out of it.