A Simple Theme On Which A Life Is Strung

I have been meaning to re-read The Art Spirit by the painter Robert Henri and today I brought it along to lunch. I was lucky to emmediately find the part that spoke to me as a young woman and today still:

Is it not fine to see the development of oneself? The finding of one's own tastes. The final selection of a most favorite theme; the concentration of all one's forces on that theme; its development; the constant effort to find its clearest expression in the chosen medium; an effort of expression which commenced with the beginning of the idea, and follows its progress step by step, becoming a technique born of the theme itself and special to it. The continuation through years, new elements entering as life goes on, each step differing, yet all the same. A simple theme on which a life is strung.