Some relationships just don't work out, no matter how bad both parties might want them to. Sometimes time, distance, and circumstances get in the way. And sometimes we have a purpose for our lives that couldn't be fulfilled inside the bounds of that relationship.
The more we take the welfare of others to heart and work for their benefit, the more benefit we derive for ourselves. This is a fact we can see. And the more selfish we remain and self-centered, the more selfish our way of life is, the lonelier we feel and the more miserable. This is also a fact we can see.