Confidence comes and goes
You expect all adults to have a boost of confidence but that is not always the case. Confidence is a rollercoaster, it comes in waves with highs and lows and that carries on in to your adult life.
You stop caring what people think as much
Ok, this does not mean you completely stop caring what your next door neighbour thinks but what it means is that you care less about the strangers. I developed the mentality that as long as my family and friends are happy with me and my actions and life choices, no one elses opinions matter to me.
You eat more healthily
I never disliked fruit or vegetables but as I ventured in to my twenties I became more conscious about what I putting in to my stomach. My eating habits changed, I now opt for fruit compared to a chocolate bar.
No matter the job, starting out is tough
When you finish university and looking for your first full time job regardless of it being in advertising or accounting, starting out will more often than not involved a lot of hours and graft. Feeling it? If it will help you get to the place where you want to be in your career, push through it, it will be worth it.
Corrie put it perfectly, as an adult you are constantly tiered regardless of how much sleep you get. Gone are the days when I can go to sleep at 1 and wake up at half 5 without feeling it that evening.
Being an adult has aspects that are fun. It honestly is not all doom and gloom but it has thrown me some curveballs.