i'm becoming an adult soon, what are things i should be prepared for?

i'm still a little years before i legally become an adult, but because of my school system and my birthday, i'll be graduating next year (when i'm 16) and starting university (also at 16 but my birthday is at the end of the first term so i'd be turning 17). i want to be prepared for life as an adult, but i'm not very intelligent and i can't understand a lot of things so people tend to be impatient with me, haha. it would be nice if any fellow mangago users could give me a word of advice :)