Lots of warble in it.
Basically, it explains that some people have learned to protect themselves against predators/abusers to the extent that they don't manage to insinuate themselves into their lives, because every attempt to breach a boundary is noted and resisted.
Others haven't been given those tools, so are more vulnerable.
The key to not getting into successively abusive relationships is to learn to recognise those boundaries and repel the predators before they are harmed mentally or physically. To recognise that they don't have to accept attention when they feel uneasy, that they have the right to make their own decisions, etc, etc.
The Big Bang Theory explained it as not having an effective deflector shield, like on the Starship Enterprise. It's the same principle.
Hope that saves a few people the effort of sorting through the chaff.