Why is it that...

...I can think a manuscript of mine is total junk, move away from it for awhile because I'm disgusted and then come back to it and find a work of art?  I just reread the last manuscript I worked on and couldn't have been happier.  It flowed.  It was witty.  No passive voice.  Good sentence structure.  Man.  Why did I stop and get out of character?  Now, I'm finding it impossible to get back into it the way I was.  UGH!

Anyone got any pointers?  I'm losing a good book as I type!