How do I come to terms with turning 18?

For some reason, when I think about the fact that I am turning 18 this summer, it makes me feel so sad. I don't want to say goodbye to my childhood. And even though 17 is not exactly a "child," it is still not an adult. I know I can't avoid turning 18 as it's going to happen whether or not I would like it to, but how do I come to terms with it? I feel like I am entering into a world of responsibility that I am absolutely not prepared for and I feel like I am leaving behind all the good things that childhood had to offer. I am also feeling some regret for things I didn't do/didn't get to do while I was a child. All of this is just making me feel so worried for the future and makes me yearn for the past. Sometimes, I would just like to stay where I am right now. I know that this sounds very dramatic and that I can't avoid growing up. But does anyone have any advice on how to come to terms with it and/or make the best out of it?