It seems you've finally caught yourself a break. Don't let your scared side take over and ruin a good thing. You've got an opportunity in front of you that you didn't think you were worthy of. Maybe, just maybe, you are. Don't be a perfectionist; at first you may need a little work. After all, you know little to nothing about the world you're breaking into. Be patient with yourself and remember that good things come to those who wait. If you keep doing that next right thing you can't go wrong. Show up for life and the impossible may become possible. Up until now you've worried that you ruined your chances at this sort of thing because of your disheveled past. You were wrong. What you were is not what you are. Maybe one day the negative thoughts will finally completely dissipate so that you can be that best version of yourself more often. Take each day and use it as an opportunity to face your fears and get creative. You're good at that remember? What you're doing isn't rocket science; it isn't even something you've really aspired to do; but guess what? It's something that you're naturally good at (or so they say): it gives you the chance to communicate, to be heard, to be challenged...and to drive around in a car you don't pay for. Being a self-employed novelist doesn't come with a perk like that. And hey, you never know, you could find great writing material in the characters you meet each day.
The world is your oyster.
To others, a new chapter like this may not mean this much. But that's their loss. Every new opportunity in your life is a blessing and a half.
Most of all --- don't f*ck this up or I'll kick your ass b*tch.
Love you more than you let yourself believe,
* my pre-interview jam