Do dreams have to be reachable ?

I love books. Really, if I could, I would just jump into my favorite ones and life in it forever. But I can't, because I don't have the Power to do things like that. Even though it would be the best thing that ever could happen to me (yes, I think i'll never be the doctors companion and travel trough time and space with him and the TARDIS). So this could be the best thing ever.
But even this idea looks bad. Maybe I should stop having dreams which could never happen. Maxbe I should have some dreams like meeting Benedict Cumberbatch, Jennifer Lawrence, Josh Hutcherson… and so on. What ? You  meant something else ? What ? Reality ? What's that ? You're funny. I never heard  this one before! And that's me every time someone tells me about dreams and what they want to do. Don't get me wrong: I admire people who know exactly what they would like happen and what they want to do. I just never had this knowing about very thing in my life. And to stay true: I never really wanted that. I was happy with my happy, childish dreams and don't want to think about the  future and my future job. My future life. Everyone who saw Back to the Future 2 that we're going to have flying cars next years. And Hoverboards. And all that stuff.
It might sound silly and a bit selfish, but I don't really want to think about the environment issues, because I kind of want everything to stay exactly the way it is. And I know that these are childish thoughts, because everything changes so fast, but it is what I think. Because I think that I'm deep down my brain, I'm a little five year old, who likes dolphins, Teddies and Childsongs. (and deep down there I still love them). Sometimes I hate being that way. But with every day I grow older and I'm starting to think that I'm good the way I am. That the way I dream is  exactly the way should dream, because who ever made me (and if it's just my parents having sex, that's  fine by me) he or her or it thought that it made sense. So i'm going to trust the person, because for this person it made totally sense so i'm trying to understand and appreciate what they did.