Every few years, I take out Johann Joseph Fux's (1660-1741) The Study of Counterpoint and work through his species counterpoint exercises. Every time I return to it, I get more out of doing the exercises and evaluating them along with Alois and Joseph (the teacher and student who engage in the Socratic dialog in the book).
The idea that there is a "best way" to do a counterpoint exercise used to bother me. Now, after having years of experience searching daily for the "best note" to put in a given place in a piece of music, I appreciate someone (I know this someone is both fictional and would be long dead if he had been real) telling me why my particular solution to a particular music problem is not the best possible solution. Try as I may, I do end up making some of the mistakes that Joseph the student makes in the Fux exercises. Of course Fux himself spent a long time looking for the best possible solutions when he was writing the book. I am grateful for his hard work. After doing a few counterpoint exercises, my mind feels like it has been sharpened. I feel like I am more efficient when I write music, and I feel that I am more aware of voice leading in the music that I am practicing on the violin and the viola.
Now, more than thirty years after my introduction to the study of counterpoint (my teacher used Fux, though I didn't know it at the time), I really appreciate the value of being able to look at music on a note-against-note basis. When I do these exercises, I find myself in excellent company: Telemann was the first person to make a public announcement about a German translation (from the original Latin) that Haydn, Mozart, Beethoven, Albrechtsberger, Schubert, Brucker, and Brahms would later use. Fetis translated it into French so that Cherubini, Berlioz, Meyerbeer, Chopin, Rossini, Auber, Paganini, Moscheles, Hummel, and Liszt could use it.