I think "The Secret" is ridiculous, personally. They claim that the "law of the universe" is that like attracts like. Any science class will show that it's completely the opposite. Opposites attract. The only scientific thing I can think of that would be close is the "like dissolves like", and even that is because of opposites attracting.
Someone gave my mom that book when she had cervical cancer, and she felt like it was kind of rough that the book was basically saying that she must have given herself cancer by thinking about it, somehow...
I don't believe in the Secret either. But I do take something from it. I do think that thinking positive helps with the healing process, whether youer healing from disease or trauma or whatever else. Although I don't think negative thoughts give us disease, I do think they can slow our healing process.
The opposites attracting you're talking about relate to magnetic poles and electrons/protons and so on, but I think the attraction they're talking about here is different. It's the same attraction that happens when you pluck a guitar string and the piano note of the same pitch resonates with it. Now whether that speaks to how the Universe works, I don't know if that's necessarily the case, but I think there is a distinction between magnetic attraction and resonating attraction.