In a post about the differences between being a graduate student and professor, one of the authors over at orgtheory.net makes a point that seems applicable almost everywhere:
In the early years, critique is about identifying holes and mistakes that make ideas less plausible. In the later years, critique is about identifying the germs of ideas worth development despite the current holes and mistakes. The shift is subtle and took me a long time to identify.
Sometimes I suffer from this myself.