In legal terms (at least in my country) you are considered an adult when you are 18 years old and, then, you have to take relevant decisions about your own life. But legality doesn´t decide when you are prepared to be a mature person. I think that the main important university to be self conscious about the meaning of life is life itself.
It´s said that a middle aged person gets through a crisis because all he has built starts to fall down. Then, enjoy your age!