There are survivors...

You can admire their resilience. You can feel as if have been there too, in other times. You might have a real appreciation for a soul who has seen some things (military life, crazy upbringing, survived abusive situations etc.) and see how parts of their experiences overlaps with your own tough experiences. We are here to be creative, but we have different ways of going about it sometimes. Sometimes an undernurtured, overcriticized child carries the pain as an adult and you can still feel for the person but you could get run over by their hostility just because you could have a productive time when the part-time delightful personality who can be fun and receptive decides to show up on a sporadic basis. Also such a person cannot be there for you when too much of their own agenda is always ruling everything.