The mind (or psychic system) becomes a machine for producing misery. The unhappiness (or happiness) isn’t a direct result of some external reality or cause; it’s a production of the mind. If a doctor tells me I have cancer and will be dead within six months, my reaction (whatever it is) is self-produced; it’s not caused by the doctor’s words. There is no reason why I can’t react with laughter, relief, happiness, or any other emotion. This is what self-determination means.
These experiences can be called system operations. The mind is a system that carries on specific operations, a machine that produces specific affects. No two systems carry out the same operations.
One of the principles of Buddhism is that we produce our own suffering, and if we recognize this fact we can stop doing it.
Human beings have created the negative. The negative is what doesn’t exist or what isn’t experienced right now. If I experience a dark, cold winter day, I might imagine or wish for some other kind of day. This other kind of day is the negative; it’s something other that what I experience right now, and it’s unattainable right now. I can remember such a day or anticipate such a day. I might try, instead, actually experiencing the dark, cold day rather imagining or wishing for some other kind of day.
Or your problem might be fear. This is something Jean Klein said about fear:
Look at your fear; become very familiar with it. You don’t really know your fear; you know only your idea of it, your memory. You must face the actual sensation of fear, in the moment itself, when you are in the fear.