Many people before me have spoken of what an odd business this writing thing is. The relationship is between you and your pen/cursor, alone in a room, locked up together (if you're in the process of A Project) 24/7 (or so it can feel). It's like a drug, or a transcendent experience, or a love affair, sometimes. At other times it resembles something dysfunctional and distinctly suspect; the kind of relationship you'd counsel your best friend to escape from.
Then there's the underwhelm when it's actually out there, and you have no idea if anyone's reading it; plus it's a long time to the first royalty statement and a longer time again till the first royalty payment. If you were paid an advance, as I was on my first two books, both put out by relatively big players in the publishing field, it takes a year or two to offset that against royalties, especially if your work is 'minority interest'. With the smaller publishing houses, with no advances, the royalties, in my experience, are in two figures, or the low threes. In other words, it won't keep you even in the style of poverty to which you'll need to become accustomed.