The pre-op liquid diet is an emotional roller coaster, that's for sure... but most people will tell you that, if you stick it out, it DOES get a lot easier by about Day 2 or 3. That was definitely true in my case-- the first 48 hours were the worst, but I just kept telling myself, "this isn't going to last forever," and reminding myself that the point of the liquid diet isn't just as a "test," but more importantly it's to shrink your liver and thus make surgery safer.
So every time I thought about cheating, I pictured having an enormous beach-ball-sized liver inside me that my surgeon would surely "nick" and I would bleed to death on the operating table. Is that cookie worth dying on the operating table??? I dare say NOT.
You've got to start telling yourself YOU CAN DO IT. 10 days is not the end of the world-- it's a tiny blip of time in relation to the rest of your life. Really, 10 days is NOTHING; it's barely a hiccup on your journey. The more you stress about it, the worse it's gonna be.
(But to answer your last question, YES-- being anxious about it IS extremely typical!)