Not only about trust issues though . For some people a boundary would be using recreational drugs . Perhaps another example may be where the other person starts believing in a cult , or if if both people are religious and one of them lose their faith . You can see how these are boundaries that have little to do being property , but violates the original mutual bond in some way . Of course we cannot expect our relationship partner to always agree with our view of things , but we do have a right to withdraw ourselves from a relationship . Closer to your point , what about one partner wanting to have an open relationship at some point ? And of course we can move from there to more and more nuancedrestrictive boundaries . yes , where is that line between possessiveness and trust then ? Which is I guess your point . Not sure , but I guess there are a variety of cultural and societal rulesexpectations that come into play .