The true value of money.
I first realized this when I finished my degree, and found out exactly how much money I owed in student loans. I remember filling out my first student loan application, with no true understanding of the amount I was asking for. Then, two, three, four loans later, I am handed the bill for just over twenty grand. I was incredibly lucky to find a decent paying job only five months out of school, but at this rate, it will still take me up to five years to pay it off.
This is also the first time that I have ever lived completely alone and independently (wow! - I just realized that when I typed it). Unlike the last seven years, when all expenses were shared evenly with a roommate, I am for the first time feeling the financial strain of paying all my bills, all by myself.
But, having said all this, I make ends meet - I feed myself wholesome food, I indulge occasionally, and I am happier now than I've ever been.