Examining the terms selfishness and unselfishness in their broader context, one can see that they applied directly to the idea that man has two natures. Selfishness belongs to man's lower nature; it stems from and is deeply embedded in the biological world, the mechanical world, the world of reflex action and thoughtlessness. Selfishness can pose as thoughtfulness; yet it has no need for thought, since it obeys the biological imperative.
Unselfishness is very different. It always involves awareness and thought in the first place, since it requires an individual to sacrifice — meaning to both give up and to make holy — their own interests in favor of another, which goes against the lower force of law. It is an upward movement; it reaches towards a higher principle, it engages the concept of betterment and puts it into action. One is unselfish in order to make things better.
Unselfishness belongs to man's higher nature and is inextricably tied to our effort to reach towards heaven. This is why it makes sacred; this is why sacrifice is an unselfish action. It mirrors, upside down and from the opposite direction, the sacrifices that created this universe and the love that was given up freely and unselfishly in order to give us life and make us what we are. It costs something for us to be here; and an enormous sacrifice has been made in order to create the universe in the first place. All of material reality arose from a supreme action of unselfishness on the part of the Lord; and every action that mirrors that, honors it, and turns it back towards itself is a holy and sacred thing, since it aligns directly with the original purpose and will that creation arose from.
It may seem overly simplistic, but will we say that man has two natures, we don't need to necessarily think about all of the unusual higher energies we are able to receive income into alignment with. Before any of that means anything, we can see our two natures from the perspective of selfishness and unselfishness; and in every case, when we act on behalf of our own selfish or higher nature, we act more consciously. We make a choice to try and make things better; not just for ourselves, but for others, and other creatures — even the planet.
Of course these impulses go astray in countless ways. Because our natures are locked in a struggle with one another, there is always a tendency for selfishness to degrade the action of unselfishness. It is in its nature to do so. This is why it takes constant effort to be more than we are.