Actually with practice, controlling your dreams is indeed completely do-able. Lucid dreams are hard to manipulate but get easier with time. I used to be plagued with nightmares (and I mean screamers!) one in particular which was a recurring dream. I practiced a long time but once I changed the course of my nightmare while dreaming, I have never had that nightmare again.
Everybody has no doubt experienced a lucid moment in a dream that seems so real, where they realize they are in fact dreaming, it is then that you can manipualte your dream. The hard thing to do is stop yourself from waking up.
Learning the skill to control my dreams was very useful to me, but as long as they are not scary, I prefer rolling along with a dream and seeing where my mind will take me. There are loads of books about controlling dreams, which teach you how to be aware of and manupipulate dreams.
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"London is a city coming down from its trip and there's going to be a lot of refugees"
- Danny,Withnail & I