I have decided that editing is a lot like riding a spinny ride. Not a merry go round that's slow and plays fun music, but one of those rides that spins backwards with loud booming music and a DJ yelling, "Do you want to go faster!"
This is the way it goes (at least it does for me).
You start editing your book. After reading through the first five chapters you notice that you're using too many adverbs, so you start watching for the dreaded "ly" words. By chapter six you realize that you over use the word "around", so you highlight each one and try to find a different word, or take it out all together. When you reach chapter eight, you see that your dialogue tags are not mostly "said". Instead they are "explained, exclaimed, asked, yelled, screamed", so you fix those.
When you get to the end, you still have to go back to the beginning and fix all the adverbs, "arounds" and dialogue tags that you missed, but as you make those corrections you find other mistakes and the process starts all over again.
Finally when you think you have everything perfect you give it to your beta readers and you realize that there is a lot more you have to work on. (Don't get me wrong - I absolutely love beta readers. I'm definitely a better writer because of them.)
That is why I think editing is like a spinny ride and right now I'm almost ready to puke.