1 week since Falling Ashes was released (Progress Update)

Okay, so it's been 1 week since I released the final installment of The Fire Mage Trilogy. 
In 7 days I've only sold 176 copies, and 20 box-sets. Needless to say, it's a little disappointing and disheartening. I haven't even made the money back it cost to get the book Proof-Read. The first week is always the biggest ... usually. Sales are already starting to drop fast.

When I published Book #2 there was a far bigger surge of sales in the first week, that's for sure. I guess I was expecting a little more, considering it was the finale.
Maybe I'm doing something differently this time. I'm not sure what. Hm. Maybe I should offer Book #1 for free for a couple of days.

Did I not promote the book enough? Or perhaps no one is interested in them anymore. I don't know. 
All I can say is; I doubt I'll be able to write full time any more if my sales don't pick up.
After all, it took six months to write Falling Ashes. My blood, sweat and tears went into it (figuratively)
How can I continue to do what I love when it so clearly isn't paying off?