I started having these "lucid dreams" when I was about your age. They were really fantastical. I don't have them as much anymore. What's really nice is that when I realize I'm dreaming in my dream I can do whatever I want. If I really don't like the dream then I tell myself to wake up, and I do (about 90% of the time). Other times, I'll decide that if I'm actually bored with my dream, I'll go do something fun like fly. Sometimes, I dream that I've woken myself up from a dream, but I really didn't. After about 15 minutes or so of thinking I'm awake, I'll realized that I'm still dreaming when something ridiculous, illogical, or improbable happens. Usually, I am able to wake myself after that.
I'm not very good at it. I have no control. When I try to fly, I end up falling on my face. When I try to snap my fingers to make something amazing happen, it doesn't happen. I always wake up mad because of all the fun I COULD have been having.