just wait till you turn 20 then 30 then 40 etc;)
i felt the same way at 18 as you are feeling! but then when i reached 20 i felt like i was really leaving my teenage years behind and it’s weird to be a “real adult” now lol! (oh my i sound like i am sooooo old! 18, 20 even 21, 22 is still young!!)
enjoy every moment of every age! and HAPPY BIRTHDAY!