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Swami Vivekanda answer this question in one of his lecture, quoting it from this link 

The next question is to know what comes after realisation. Suppose we have realised this oneness of the universe, that we are that one Infinite Being, and suppose we have realised that this Self is the only Existence and that it is the same Self which is manifesting in all these various phenomenal forms, what becomes of us after that? Shall we become inactive, get into a corner and sit down there and die away? “What good will it do to the world?” That old question! In the first place, why should it do good to the world? Is there any reason why it should? What right has any one to ask the question, “What good will it do to the world?” What is meant by that? A baby likes candies. Suppose you are conducting investigations in connection with some subject of electricity and the baby asks you, “Does it buy candies?” “No” you answer. “Then what good will it do?” says the baby. So men stand up and say, “What good will this do to the world; will it give us money?” “No.” “Then what good is there in it?” That is what men mean by doing good to the world. Yet religious realisation does all the good to the world. People are afraid that when they attain to it, when they realise that there is but one, the fountains of love will be dried up, that everything in life will go away, and that all they love will vanish for them, as it were, in this life and in the life to come. People never stop to think that those who bestowed the least thought on their own individualities have been the greatest workers in the world. Then alone a man loves when he finds that the object of his love is not any low, little, mortal thing. Then alone a man loves when he finds that the object of his love is not a clod of earth, but it is the veritable God Himself. The wife will love the husband the more when she thinks that the husband is God Himself. The husband will love the wife the more when he knows that the wife is God Himself. That mother will love the children more who thinks that the children are God Himself. That man will love his greatest enemy who knows that that very enemy is God Himself. That man will love a holy man who knows that the holy man is God Himself, and that very man will also love the unholiest of men because he knows the background of that unholiest of men is even He, the Lord. Such a man becomes a world-mover for whom his little self is dead and God stands in its place. The whole universe will become transfigured to him. That which is painful and miserable will all vanish; struggles will all depart and go. Instead of being a prison-house, where we every day struggle and fight and compete for a morsel of bread, this universe will then be to us a playground. Beautiful will be this universe then! Such a man alone has the right to stand up and say, “How beautiful is this world!” He alone has the right to say that it is all good. This will be the great good to the world resulting from such realisation, that instead of this world going on with all its friction and clashing, if all mankind today realise only a bit of that great truth, the aspect of the whole world will be changed, and, in place of fighting and quarrelling, there would be a reign of peace. This indecent and brutal hurry which forces us to go ahead of every one else will then vanish from the world. With it will vanish all struggle, with it will vanish all hate, with it will vanish all jealousy, and all evil will vanish away for ever. Gods will live then upon this earth. This very earth will then become heaven, and what evil can there be when gods are playing with gods, when gods are working with gods, and gods are loving gods? That is the great utility of divine realisation. Everything that you see in society will be changed and transfigured then. No more will you think of man as evil; and that is the first great gain. No more will you stand up and sneeringly cast a glance at a poor man or woman who has made a mistake. No more, ladies, will you look down with contempt upon the poor woman who walks the street in the night, because you will see even there God Himself. No more will you think of jealousy and punishments. They will all vanish; and love, the great ideal of love, will be so powerful that no whip and cord will be necessary to guide mankind aright.