I've written before about my inner editor who wants to edit all my words even before they are on the page. After I started editing professionally, the inner editor became annoyingly omnipresent, but after a while, she settled down into her niche in a part of my brain. Though she does show up from time to time, I am more successful in silencing her for a while, until I'm ready to summon her up.
About editing itself - there's something beautiful about getting a piece of prose to its final, presentable form. With each writer, the challenges are different. And the more I edit, the better I become at recognizing what needs to be done with a certain piece of text.
Also, there are different levels of editing. Some manuscripts need heavy editing, where I need to shake up entire passages and put them in a different form. Some need lighter editing, and some just need a once-over. But each one is difficult in its own way, and I change font styles and sizes during each round of edit to ensure that I've missed nothing. It is tiring, but fulfilling.
Besides, it is a lovely feeling when clients have good things to say about you. Quick link to my testimonial page here!