Reaper Form skill, Reaper’s Curse sub node enables you to lose health on kill. It is okay in battle but is very annoying while you are in the city especially with Wandering Spirits enabled.
You break some wooden stuff, passively with Wandering Spirits - you loose health very fast, even in the city hubs. Took me some time to realize what is going on.
Preferred solution: do not count breakble stuff as kills?
PS: Or it may be a Blood Pact passive from Acolyte which is also bound to kills