Perhaps you are just way to controlling or organized or perhaps logical. You want to do something but your sub councious is saying "you cant do that you dont know how it is or how to do it". In a dream i personally just imagine and picture stuff and i can achive basically anything i can focus enough to do. If I want to open a door in my house that will lead to outer space just imagine it actually happening just before you do it and create that mental picture. Be confident that its gonna be that way and hen you open that door... Boom outer space. Try practicing creating mental pictures while awake for example : imagine yourself shooting flames from your hand , imagine how it would look picture it and expect and want it to happen. Thats what i do and it works.