Revisiting subject matter

I don't always know how I feel about my approach to painting.  Painting the same object, day after day, feels less like "real art" and more like academic study.  Though my goal was to explore composition and light, I have found myself going down the rabbit hole of self while I work on this series.   
In the history of "real art" there are a ton of examples of artists who use the same, or similar, subject matter in their work over and over. Degas is best known for his ballet dancers. Keith Haring brought the same outlined figures into much of his work. O'Keeffe revisited the skull and bones again and again in her work.  
These three artists, three of my personal favorites, reassure me that as I repeat myself in each painting, I'm in good company.  However, I'm left wondering how these artists felt about their subject matter.  Were these images a source of comfort or a source of angst?  Did they love the act of revisiting these forms or were they trapped by the form and desperate to move forward?  Personally, I wish I could get out of this rabbit hole.