"I worked at all kinds of jobs, mostly commercial editing"

Marilyn Hacker's quote talks to the effort and commitment she put into her profession. She worked at a range of jobs, but her focus was on commercial modifying. This suggests that she was passionate about the modifying process and wished to sharpen her abilities in this area. It also implies that she wanted to handle any task that would assist her gain experience and understanding in the field. Her quote is a testimony to her commitment to her craft and her willingness to put in the effort to end up being an effective editor. It is also a tip that hard work and dedication can settle in the long run.