sigh... to go back to school after you grow up is not that easy...
1) your classmate might be like 10 years younger than you (you might not feel comfortable gar)
2) the opportunity cost will be much higher (it is quite hard to work and study full time. And some programs do not offer part time options, so are you going to quit your job? work part time? but when you grow up, you'll have a lot more expenses... Do you still wanna ask your parents for money to study???)
3) Your memories are not as good as they used to be
etc...