Sometimes negative feelings are a cause for action if they are valid. To deal with your feeling of fear, worry and doubt in the moment, simply think about what you are going to do about what you are thinking and then let go, or do it immediately if you can, so that your mind can rest on the issue. Be happy and your situation will automatically change for the better.
You claim that "positive thoughts always resulting in positive things" is not the basis of the LOA. In part you are correct. The foundational basis in science, as I alluded to in the article was that thought stuff particles travel through ether (not air) and interact with formless stuff to create whatever it is that you are thinking about. This was how "the law" started.

How To Manifest What I Desire