You are not your feelings

We are awash with constant thought and emotion. Most of the time these things come and go, passing by mostly unnoticed. But then, there's that emotion or thought that just feels so authentic, so real. And then you decide it is you. This is when stuff gets bad.
So now, you've decided that this thing makes you you. You think to yourself, "I am!" It can be a good emotion, or a bad emotion; the content of it doesn't matter because you've just set it up as a god. There is only one I AM and we are made in his imagine but we certainly AREN'T, at least not yet.
I think this is the source of some mental illnesses. At first it is a simple thing, like being sad for some actual reason. Then the primary reason for sadness leaves, but we identify with it and keep it around. Eventually, after several incremental changes, we have even managed to change our physical bodies. We certainly re-wire our brains after a while. It may even be possible that some of the thought disorders come from this. I know people think it's genetic, but people also pass on ideas to their children, so it could look quite genetic with out necessarily being so.
The evidence I have for this is anecdotal, but I have noticed that people actually diagnosed with a mental illness start acting worse than they did before they had the diagnosis. Part of it is relief, I am sure, but, especially among younger people, there seem to be a sense of power that comes from craziness. It's alluring to some. It seems to promise possibility on the one hand, but lack of responsibility on the other.
Then, of course, people get to live the reality of it, and when they finally get it, they get really angry.