I used to have horrible nightmares all the time, but then I learned how to do lucid dreaming whenever, and now I just enjoy the show. If Hillary shows up in a dream, I just laugh and ignore. If a building collapses in a dream, I just put it back together. Really, dreams are no big deal, not messages.
Certainly one can influence one's own dreams--especially with practice.
However, a long list of people historic and present are living testimonies that SOME dreams are indeed messages from God.
Joseph in the Old Testament comes to mind along with Daniel.