Changes can easily come about in all of us, even those we love and trust. When this happens, how do we keep loving them without expecting anything?
I think this is a question we all ask ourselves at some point http://buddhism.about.com/od/basicbuddhistteachings/a/attachment.htm
What Is Attachment?
In order for there to be attachment, you need two things -- the attacher, and the thing to which the attacher is attached. In other words, "attachment" requires self-reference, and it requires seeing the object of attachment as separate from oneself.
The Buddha taught that seeing oneself and everything else this way is a delusion. Further, it is a delusion that is the deepest cause of our unhappiness. It is because we mistakenly see ourselves as separate from everything else that we "attach."
Zen teacher John Daido Loori said,
"[A]ccording to the Buddhist point of view, nonattachment is exactly the opposite of separation. You need two things in order to have attachment: the thing you’re attaching to, and the person who’s attaching. In nonattachment, on the other hand, there’s unity. There’s unity because there’s nothing to attach to. If you have unified with the whole universe, there’s nothing outside of you, so the notion of attachment becomes absurd. Who will attach to what?"
Because we think we have intrinsic existence within our skin, and what's outside our skin is "everything else," that we go through life grabbing for one thing after another to make us feel safe, or to make us happy.
Living without attachment is a lot like living without trying to get some outcome in the world. It is living life but not defining ourselves essentially as a companion or a worker or a studier or being just the body.
So not being attached or not having expectations involves loosening up our own self identity that is wrapped up in the world and how it appears. If we are totally comfortable in this moment it is far easier to accept the relationship we have with that person.
Keep practicing meditation every day and have meditation be part of your relationship could be a good start.
There's a question here about being a parent (which is a kind of love).
I especially admired this answer which identifies different types/aspects of love (Metta, Karuna, Muditha).
You haven't said much in your question: it was not specific.
Depending on the change, depending on how the people and the "trust" were changed, maybe you shouldn't keep loving someone, or maybe you can't; maybe you should love them in a different way; maybe you don't control how you feel; maybe Buddhism can help you to live with less expectation.