That's pretty normal. (Of course, I see almost everything I write as crap anyway, so maybe I'm not the best judge
) After spending so much time with your manuscript, you get blind to it and can become
unable to judge it.
Maybe it's time to send it out for real?
Even as a reader, there are times where I feel a certain passage is crap, even when the first time I read it, I thought it was awesome...