I don't have any formal training in this, but I spent a three years working at a drop-in center for people who were chronically homeless (this was almost always synonymous with some form of psychosis).

The lesson I learned from those years was that I was most helpful to people when I realized that I didn't play any different role in what was going on with them than the chairs on which we sat or the steps into the building. Whatever helpfulness I provided, occurred when I didn't allow myself to feel personally responsible for their psychosis.