This is self-explanatory, since to be grouchy is to be crabby and irritable. In parrots, grouchiness is often followed closely by aggression.
Pet parrots tend to have their own ideas about things, much to the surprise of inexperienced owners. Birds that do not feel good also might disallow interaction, driving people away with aggression if the people do not understand subtler body language. Some pet birds are not particularly sociable in the morning, and owners who force contact before leaving for work frequently find themselves with hostile interactions.
Unless the house is on fire and evacuation is necessary, there is no reason to force a pet parrot to interact when it does not wish interaction.
Disclaimer: BirdChannel.com’s Bird Behavior Index is intended for educational purposes only. It is not meant to replace the expertise and experience of a professional veterinarian. Do not use the information presented here to make decisions about your bird’s health if you suspect your pet is sick. If your pet is showing signs of illness or you notice changes in your bird’s behavior, take your pet to the nearest veterinarian or an emergency pet clinic as soon as possible.