Among people who work with animals, it's called compassion fatigue, a sustained, even chronic stress on both the mind and body of a caregiver. And it has long afflicted people who can't say no to animals in need - whether in shelters, rescue groups, veterinary clinics or even among independent caregivers.
"The thing about compassion fatigue is you don't always know in the moment that you have compassion fatigue," Krieger tells The Dodo. "It takes a very self-aware person for that to be so obvious."
Instead, the weight of all those feelings - seeing animals abandoned, put down, abused, lonely - builds up over time.