Why do people say this shit when you ask how they're doing? What the fuck does it even mean? Did you really grow up dreaming of working in some corporate cube-farm or selling cell phones at a mall kiosk?
I get it when some people say it sarcastically every once in a while, but you always know when people mean it when that crap spills out of their dreamhole. I know it might annoy or worry some people if you actually said "ahhh, just living a nightmare," but at least that's an honest response. Just go with "another day another dollar" or "same ol' same old." At least then you don't sound like such a tool.
Now If someone walked in on me snorting some coke off of Kate Upton's naked body next to a huge stack of $100 bills while on a 6 month trip to the French Riviera, that's the only time I'd respond by saying... Just living the dream.