The model I prefer to subscribe to is the one others have already touched on... Rather than your consciousness affecting reality directly, it only affects your perspective of reality. Your knowledge, understanding, and viewpoints all make up a filter through which you experience reality. This is why depressed people find it easier to see things pessimistically and people in love see things with rose tinted glasses. Reality still persists and one car crashing into another will still happen no matter how much you try and influence things with just your mind. If you want to change causality, you have to use causality yourself (e.g. Stopping the crash by blowing up a big balloon between them... But you'd have to have such a balloon already at hand). Well, my explanation and example might be messy, but you should be able to understand the point. You influence your own internal reality, which is your perspective/filter/reflection of reality, but external reality is beyond that influence.