Age after 21

What come across mind when age is over 21? When still at primary, what we waiting is to enter secondary school at 13 Y.O, then take pmr at 15, spm at 17 and some might waiting for 2 more years to sit for stpm at 19 Y.O before enter Uni. Which mean that from here we saw a gap or period of time that what we do involved with time, what we plan to do when achieved that time. At age of 21 that started to gain freedom legally. It is the time where we are considered as adult, know how to make the right decision, analyze logically, socially enabling compare with during childhood. So what will you be thinking afterward since there is no specific bond as long don't against the law?
I've no idea why i writing this,
maybe is because of there is no more excitement in life since can do many stuff as long don't steal don't kill.
maybe is because i scare of getting old since a single day is enough to make us a little older.