I agree with ask996 on this one, based on the lyrics but also based on the performances by both Dolly Parton and Whitney Houston. Watch and listen, and this song is clearly a plaintive reminder that the singer may be letting go, but that release will not change the emotional attachment.
I'm not so sure that the song is selfless. Think about this, the singer enumerates all of the wishes he or she has for the "loved one" as if the relationship is over. That's nice to walk away from the one you love and leave them with well wishes and no guilt trip would be selfless. However, this is not what happens. The singer then sticks the knife in by saying I wish all these things for you, but don't forget "I will always love you." Just enough of a guilt trip to take away the selflessness.
I think pohnpei has given the correct answer. Love is selfless and sometimes we have to allow others to do things that are not necessarily what we want them to do but we know it is best for them
I think that this song is about how love is or at least ought to be selfless.
In this song, the speaker is actually taking leave of her lover. She is letting him go, but still saying that she loves him. Her reason for this is that she thinks he would be better off without her.
So what is happening is that she is sacrificing her own happiness, it seems, because she loves him. Therefore, I would say the message is that a person who really loves someone will do what is best for the other person. In that way, love is supposed to be selfless.
I suspect that the singer of the song is trying to tell to the focus of their affection that they will always love them.