You still feel like a child in your head but the truth is you're an adult now and responsible for all your actions. Start thinking about each decision before you take it.
I've been 18 for a couple of months now and I can categorically state that it's no ****in different.
Did you also have that moment where you bought the first legal pint but you weren't even ID'd so you suddenly realised you could've been doing it for months before and your life is meaningless?