Editing sucks

I don't know how book editors do this for a living.   I'm reading through my book yet again and have still found errors.  One error was a previous one I had put a mark through but didn't correct.  Another error was I used the word 'it' instead of 'he'.  Makes a big difference in a sentence when you use the right word.   Other things have been small errors like a dropped period or one letter too many.

Granted, there aren't as many errors now and I know the chances are slim that I'll catch every single error.  Knowing this, I have to say that if I published my book today, I'd be okay with it.   There aren't that many errors and readers can actually read it without cringing or having to mentally correct a sentence.  It's readable. 

I don't know if I'll have my aunt go through it one more time or not.  It may not be needed but I fear she'll find something that needs correcting. silly, I know.  

Also, for any readers I have, what are your thoughts on grammatical errors, spelling mistakes and readability of books?