Unlike most noteworthy artists, Harris never experienced even moderately serious financial problems because his family was the Harris of Canada's Massey-Harris farm implement firm. And of course he had many of the right social connections that allowed him to gain influence in the Canadian art establishment of his time.
Due to his circumstances, besides his efforts to get the establishment to accept modernism, Harris' "struggles" in art largely had to do with improving his skills. And perhaps more importantly, seeking a kind of art that meshed with his strong interest in Theosophy, a spiritual belief system that had a burst of popularity during the late 19th and early 20th centuries.
Theosophy-related concerns seem to have strongly influenced Harris's drift from representational to abstract painting over the arc of his career. The turning point took place during the years he lived an Santa Fe, New Mexico, whose art colony included other budding abstractionists.
An example of Harris' representational works.
One of his best-known paintings from the mid-point of his career where real-world objects were simplified.
Harris for a while had the habit of testing abstractions by viewing them with different orientations -- the idea being that the abstract design would hold up no matter which way the painting was displayed. I've seen at least two orientations of this on the internet. The one above is that used by the Vancouver Art Gallery, where the painting resides.
One of his most strictly geometric works.
Drifting from Geometry.
A more "organic" look is now in place.
This was painted around the time Harris had a heart attack. By the time he died, he had developed dementia and his final painting were of blobs built up with wispy strokes somewhat like is seen here.