I'm what you would consider an "adult", and I have been for awhile now, but I really don't feel like one, and I definitely don't act like one, either.
I still do things that I know would make my mom sigh and shake her head at me because she really thought she raised me better. But come on, if I drop an ice cube on the floor then of course I'm going to kick it under the refrigerator. That's just common sense.