I have found that after watching the secret, there are many laws of the universe we may not be aware of or intuned to. Just like the law of gravity, we see it, we know it exists, yet we work and live around it. Still, our mind does not have to think about it, it's just there, good or bad, like it or not.
Hold your mouse out in front of you, and now let it go and it will drop. See, you won't do it because the law of gravity might break your mouse. So we work around the laws of the universe to make them work for us. I believe there are many laws of the universe we don't understand, we can't see or that we aren't even aware of. The law of attraction is just opening our minds to how powerful they really are.
To even question if the law exists, is to use "this secret" in the wrong manner. Changing your thoughts to appreciation, happiness, and desires creates a positive energy that people and the universe pick up on. I don't see any harm in trusting that "seeing is believing" but first, we have to see it in our minds.
Einstein said it best, and I quote, "If you think you can, or if you think you can't, either way you're right!"