Congo African Greys are known to be prone to plucking and such... but my Gympster never has... he has moved from me in New Mexico to Indiana to live with my parents when I went to basic training, then he lived there for a year and loved my mom, then moved back to me now that I am stationed in California. He's the same boy he's always been. He was upset with me at first, but he decided it wasnt worth not gettin attention... so he's all into me again. The only thing that has ever gotten to him was a vet that did 'birds too' who used a plier thing to cut his beak and clipped his nails to the point a few were bleeding, and HORRIBLY clipped his wings... that vet was the only person he has ever growled at, luckily the REAL bird vet he went to right after that fiasco was a woman, and really nice... he learned his name that day, and was back to normal... so always go to a REAL avian vet! That was the only time he stopped eating, though he didnt pull feathers or anything. Sorry went sorta off-topic, but i had to rant.
I think it depends on the bird himself, he takes most things in strides... especially if there is a *small* piece of sharp cheddar in the future.
...though maybe it helped that my mom spoiled him ROTTEN!!!
also... i never kept up any certain schedule or anything.. so he was used to new things and daily happenings. I think that helped.