When we went away this weekend, we had to leave Cleo at a cattery for the first time. It would have been better if we could have asked our neighbours to come in and feed her for a couple of days, but for one reason or another, that wasn't possible. Luckily, we have a wonderful cattery not far from us, run by very caring people, so we knew that she would be in excellent hands.
When we opened her carrying box in her new lodgings, she really didn't want to come out. When she did, she walked into the run and immediately started hissing and growling at the cats in the neighbouring runs. One very portly black and white cat in the next run wandered over to her in a friendly way in response to this hostile greeting, which only made things worse. Cleo was not at all happy, and it was clear that she would have to be moved to calm her down, and also so that she didn't kick off a huge riot among the other cats being boarded. This caused a huge amount of hassle as other cats had to be moved, runs cleaned and so on, but eventually she was housed in a run with opaque walls so that she couldn't see any other cats.
She still wouldn't come out of the travel box, but looked out of the window of the inner room at the peacocks and peahens strutting around outside and trembled like a leaf. I think she thought that these huge birds were going to kill her, and looked up at us with big, 'take me home now, please' eyes. We felt truly dreadful leaving her there, but we had no choice, and it was only for a couple of days. The problem is that you can't explain to cats (or dogs) that they will be perfectly safe and comfortable and you'll be back to collect them in two days. When the cat in question is rescued and has had a lot of traumatic upheaval in her life, you feel even worse.
She did eventually settle down, but was still lying on her bed inside her travel box when we came to pick her up -- probably for maximum guilt-inducing effect. She seems pretty happy to be back on her own territory, and has been sniffing everything, rubbing up against every available surface (including us) rapturously, and purring like a mad thing.