The mind's capacity is limitless, and its manifestations are inexhaustible. Seeing forms with your eyes, hearing sounds with your ears, smelling odours with your nose, tasting flavours with your tongue, every movement or state is all your mind. At every moment, where language can't go, that's your mind.
The sutras say, "A tathagata's forms are endless. And so is his awareness." The endless variety of forms is due to the mind. Its ability to distinguish things, whatever their movement or state, is the mind's awareness. But the mind has no form and its awareness no limit. Hence it's said, "A tathagata's forms are endless. And so is his awareness."
Bodhidharma
The Ultimate Principle of Reality - All that has a form is illusive and unreal.
The belief you have a terminal illness can actually cause you to die, and negative thinking is much more common in our current world.