I felt like I was a 'grown up' many different times:

-when I made my first car payment
-when I made my first car insurance payment
-getting my first credit card statement
-teaching my first freshman seminar class
-seeing my 'little' cousins graduate from high school

But this was the real big one...

Finally realizing that a lot of what my mom used to tell me [IT'S FOR YOUR OWN GOOD!] was true...and it started to make sense. I find myself telling my nieces and nephew that now.