I'm sure you get the "oh, you build sand sculptures, how fun!" comments (like I do about jewelry) and it's so the opposite. People have no idea how stressful earning money from craft is.
Don't freak out, and remember to breathe. As for the mail, I had a package notice last week that totally freaked me out, knowing it was a repair (I hate it when my stuff breaks). When it finally came, it wasn't even my piece. The gallery accident sent me another artist's work. All that worry for nothing. So, the letter may in fact be nothing. And, if it is something to deal with, you will. Worrying now won't help at all.
'02 Eddy Merckx Fuga, Selle An Atomica
'85 Eddy Merckx Professional, Selle An Atomica
'10 Soma Double Cross DC, Selle An Atomica
Slacker on wheels.