If the individuality is unconscious, there is no psychological individual but merely a collective psychology of consciousness. The unconscious individuality is then projected on the object, and the object, in consequence, possesses too great a value and acts as too powerful a determinant.
Source - C.G. Jung, Definitions (Imago V. Subjective Level). CW 6: Psychological Types, par. 755.
Projection is the means [mirror] by which psyche autonomously realizes itself. It is the mechanism through which the unconscious becomes conscious. This can happen when we first meet someone. We see the traits in the other person which belong to our own psychology. Projection usually requires a hook; there is something about the other person onto which we can hang those traits.
Source - Jesamine Mello, The difference between Jung's Participation Mystique and Klein's idea of Projective Identification. Jungian Analysis & Counseling blog: Integrated Psychodynamic Approaches to Life.
We all have hooks, you have to look for the hook in yourself as I do. Projection is a terrific force. You are moved by it and you do not know why. The impact of the projection comes at you like a billiard ball. Through projection terrible things can be brought about. If you do not know of the hook in yourself or of the open door, then the devil creeps in (the projection) and has a tremendous effect. You cannot be indifferent to a projection. It is just as important whether I am projecting into someone else or someone is projecting into me. It functions in both cases with almost mechanical effect. From projections there can arise the most amazing and inexplicable things.
Source - C.G. Jung, Dream Analysis: Notes of the Seminar Given in 1928-1930 by C.G. Jung (Princeton University Press 1984). Lecture VIII: 13 March 1929, pp. 164-165.
Art: Katrine Storebo, 'Beatrix & Maimie'