Recently a young, fresh out of school artist (working at Starbucks) in New York City contacted me for advice about how to jump start his career. He'd had some good assignments as an illustrator, but things have slowed greatly recently and he needs help.
His question below stems from my asking him if he is thinking of changing careers at this slow juncture, and finding a more lucrative "regular" job. A lot of succeeding as an artist is having an extraordinarily thick skin, stamina, and patience. It is not for the faint of heart or those vaguely motivated.
I am not at this time considering changing careers. Yes, I am young. Yes, I am poor. If either of those sentences changes, then I'll revisit the subject. Until then, I hold firm to something my mother told me years ago, when I first expressed interest in commercial art -- that illustration is the business of the last man standing. If I can just hold on long enough, it will work. I will outlast the others because whenever I pick up a pencil or a paintbrush, I know that this is what I was meant to do. Whenever things get a little dry (right now would be a good example) I always toss options around out loud. I never really mean any of them. I'm here to stay.
Being young and unencumbered (forgive me, I don't know if you're married and/or have children, I'm just guessing you're not) is the best way to start building a career in illustration. Your mother is exactly right - it takes almost unlimited perseverance at first. There will be weeks and months (and of course, weekends) when you have so much work you won't have a minute off and yet you can't afford to turn anything down; and then a dry period will test your commitment and make you get back to marketing all over again.
The harder you work, the better you'll think, the freer you'll create, the more confident you'll become, and the more likely buyers will trust that you will do a terrific, professional job on time and on budget. They will trust you to make them look great.
You sound very self-aware of how you feel about being an illustrator. That's essential, because if you can't convince yourself that what you're doing is worth it, you won't convince anyone else.