This means that you have a very active imagination. I had a dream that I was 21 again and then I was crying because I knew I couldn't stay there in the dream........just really weird. But it means nothing really. Sometimes, the mind uses dreams to help you escape from reality at least that's what happens to me. Many teenagers experience depression on some level so if you have any mood changes, or are feeling depressed or like you want to kill yourself in reality - you need to see a doctor because you could have a chemical imbalance of the brain which is easily treatable. But, if you don't have any depression symptoms this is probably just symbolism because you feel that you want to escape from the pressures and pain that are in your reality right now or the stress that you perceive will be there when you are older. In any case, you're probably wishing that you could escape from the normal process of growing up with all of the pain, pressures and stress that come with that. It's really good to talk about these things with a friend or a social worker at your school. They are trained to be good listeners and help you work through some issues regarding your future.