1. Bills, bills, bills
This means that you actually have a designated area where you keep your bills, because you need to keep track of them so that they get paid on time. And no,
Netflix is not a bill, it is a luxury you are willing to pay for. It is something to get your toes wet in the deep water of debt. Neither are any of the other things you willingly sign up for that cost money (money that you probably don't have). By bills I mean rent, electricity, gas, cable, phone, credit cards (that are under your name), insurance (car and, if you're really adulting, health and life), etc.
2. Your parents no longer feel bad that you're broke.
The
moment you complain to your parents about all the bills you have to pay (some that if you still live at home they assigned to you) and they ignore you or feel no sympathy for you because they just do not
care anymore. This is also around the time that they stop offering to buy you stuff like food, school supplies, clothes, gas for your car, things that you didn't realize how much they amount to until you started paying for them.
3. You're the responsible one.
All your friends think you're the parent in the group and they don't even bother inviting you to things, because they know you'll probably be working to pay those bills. You're also the one they go to for advice on how to be a responsible adult because you're not intimidated by the thought of responsibilities. In other words, you are the Monica Geller in the group. You also start feeling really old around your friends, even though you are all the same age.
4. You have an agenda and master schedule.
If you have an agenda that has little to no blank space in it, it's most likely because you are busy for the next 10 years of your life. Not only that, but you create more than one master schedule for you and the people in your life (friends and
family) so they now exactly what you are doing day in and day out.
This could also mean that you have OCD and need to organize every aspect of your life.
However, don't be fooled into thinking that having your life scheduled means that it is all put together because the reality is you probably have all your time managed so that you don't have to think about the hot mess that has become your life.
5. You know the struggle of budgeting.
This means you either have a checkbook or a notebook with all the payments you have to do in a month so that you can figure out where your money is going and when. It also means that every paycheck is sorted out before you even get it. And you start budgeting splurges because there a chance you have to make the choice of getting that super cool thing you saw at the store and buying food to feed yourself something other than a cup of noodle soup and crackers.
6. Older adults like you.

When older adults constantly tell you how responsible you are and you no longer know if they are complimenting you or insulting you. Not to mention that they openly tell you they like being around you because you are not like other "kids" your age. Before you know it you find yourself having a specific group of friends that are 10+ years older than you and you are completely okay with it.