Here’s the Dream Control Training Course.
When one becomes lucid it’s usually very overwhelming. One’s trying to do something, anything, very fast because you one’s scared that will lose lucidity and won’t be able to do anything. At that point it’s important to calm down.
You practice meditation, you should know something about that 
and when you menage to calm down start with easy things. Something that is not cool, something ordinary, boring, earthly - so to say. When you menage to do that and maintain lucidity at the same time then you’ll get the boost of confidence and then you can become more brave, try harder things and so on.
What helps me is reminding myself constantly that I’m in a dream where I’m the one that makes things happen. Builds confidence and also it keeps me in the moment which is important.
Like Letaali said, doubt is your enemy. The moment you start to doubt yourself it won’t work, there will be some invisible force preventing you from doing things you wanna do. But that’s you and nobody else.
Be one and become one with the dream… Good luck!