21? Really?

It's like yes, you're no longer a kid when you reach 21, but what? you expect me to miraculously grow up in one night? start acting all mature and "be an adult"? really? i've asked people whats the big deal about being 21? and trust me, i got some quite ridiculous answers.. but in the end yes i'm 21, so just give me a break and stop using that against me.