Life has taught me that you can't control someone's loyalty.
No matter how good you are to them, doesn't mean they'll treat you the same.
No matter how much they mean to you, doesn't mean they'll value you the same.
Sometimes the people you love the most, turn out to be the people you can trust the least.
It's heartbreaking when you come to the realization that the person that was so important to you, that you trusted with your life, was not the person you thought they were. This is a difficult lesson to learn.
Everyone does not have the same beliefs, ethics or principles. There is a multitude of reasons you might find your beliefs clashing, from cultural to behavioral. The fact is you felt that you could trust someone, they were very important in your life and you found that your feelings were not reciprocated. They have not valued you or treated you with the respect you deserve.
Usually, it's expectations that create the problem, you decide how the person will be and how he will act and then experience deep disappointment when it's not the case. "Expectation is the root of all heartache." Shakespeare. You may have given him your heart but there's no guarantee that he will cherish it. You only wanted what you deserve, but you were expecting it from the wrong person. Not everyone can live up to your expectations.
All you can do is accept people for who they are and determine if they can fit into your life or not. Sometimes you get hurt, not everyone will know how to treat you, but that's how you learn what you deserve and what you really want.