I've found there are generally four stages to my own designs:
1. This is shit
2. Okay, I'm getting somewhere
3. This is pretty good!
4. This is shit
I don't know why, but if I look at a design for too long I end up hating it, even if I liked it initially. So I try to get away from my work quickly if at all possible.
As an animator, this happens to me often - even if the stuff is good!
After you view something for hours on end, your mind become numb to the nuances that make it great. On a tight deadline there isn't always the luxury to actually get away from it. My solution is to look at some work of other animators that inspire me - but only for a couple of minutes - then go back to my animation and prepare myself for the "Single Viewing Moment of Truth". I get one or two truly objective viewings of it until my mind slips back into the abyss, so I keep my pen in hand ready to scribble notes about what I see.