I miss being a little kid?

So, there used to be a time where I had friends, a dog, good grades and every day was pretty good. Now that I'm 18 I never felt so upset, missable and realized that the prime of my life was when I was a kid. I don't want to grow up because now I barely have friends, I have no goals. All I do is watch YouTube videos all day and think about how good I used to have things when I was younger. I used to have so many friends, I used to have it pretty good and now I just think about how good things used to be. If I could go back to be a kid I would. Things used to be so great, I used to be a writer and everything. In a way I feel like my life is over or as if I've already lived life to its fullest. I feel like I've been in high school forever, high school is awful and I feel like I'm never going to graduate. I feel like I just have to accept my life as it is now and I have to accept that my life will never be great or happy again. :/