One has to remember particularly that the concept of the word 'self' differs, diametrically in different references. In self-interest, it indicates the interest pertaining to the body-mind complex wherein the physical and mental pleasures are indicated. The body desires some sensual pleasures and the mind aspires for supra-sensuous happiness.
But in the word – "Self-realization", the word 'Self' means something different from the body-mind complex. The "SELF" here means, that energy which existed before this body came into existence and that which will continue to exist even after this body perishes and that which is the residue of the personality of a man after his body-mind has been removed. Thus this "SELF" is different from 'self'.
The activity, service, work done for self-interest is of a baser type and is no service at all in the real sense of the term.
From this view point we should see all the works that we are doing. It will definitely help us in truly understanding what is meant by 'Each soul is potentially Divine' by Swami Vivekananda.