Art wouldn’t exist without emotion. Art is fundamentally an expression of emotion — an expression of the artist’s inner world.
Instead of reflecting states of the external world, art is held to reflect the inner state of the artist. This, at least, seems to be implicit in the core meaning of expression: the outer manifestation of an inner state. Art as a representation of outer existence has been replaced by art as an expression of humans’ inner life.
Similar to journaling and psychotherapy, it is a way for an artist to process their feelings through a medium of music, literature, painting, etc. More mechanically, art is combining elements in a new and creative way whether that be tones in music, words in literature, paints on canvas, etc.
There is a fundamental dichotomy in expressing the emotion and marveling at the expression of that emotion. For the artist, the process of making the art is the cathartic part and the part where the artist expresses their emotion. The produced artifact, the expression, is what others view as art.
Artists, having been perturbed at the inarticulateness of their “ideas,” now feel relieved because they have “expressed what they wanted to express.”
The point of viewing art is to feel something. To feel and get a glimpse of what the artist’s inner world is like and how that relates to our inner world.