The principle for Day #13 on the 101-day book report says: "Your thoughts create your reality."
We've all heard the story of positive thinking, but this is really something much different. If I had to describe it on a cocktail napkin, the theory is that your consciousness is connected to the universe. So whatever you think about, the universe serves it up in your life.
As an example, say you're lamenting on and on that your spouse is a nag. Since this is what you dwell on, this is what you will continue to get. The universe only picks up on the subject matter, not that you think the subject matter really sucks.
The good news is that we can put this theory to work for us.
I have an photomat envelope on my counter. Whenever I catch myself thinking about things I don't want, I picture myself dropping the negatives in there. It's a dumb exercise, but the world is full of images that no one meant to develop.