From Chapter IV of Para-Bhakti or Supreme Devotion of Volume 3 of Complete Works of Swami Vivekananda

Here are some of the forms in which love manifests itself. First there is reverence. Why do people show reverence to temples and holy places? Because He is worshipped there, and His presence is associated with all such places. Why do people in every country pay reverence to teachers of religion? It is natural for the human heart to do so, because all such teachers preach the Lord. At bottom, reverence is a growth out of love; we can none of us revere him whom we do not love. Then comes Priti — pleasure in God. What an immense pleasure men take in the objects of the senses. They go anywhere, run through any danger, to get the thing which they love, the thing which their senses like. What is wanted of the Bhakta is this very kind of intense love which has, however, to be directed to God. Then there is the sweetest of pains, Viraha, the intense misery due to the absence of the beloved. When a man feels intense misery because he has not attained to God, has not known that which is the only thing worthy to be known, and becomes in consequence very dissatisfied and almost mad — then there is Viraha; and this state of the mind makes him feel disturbed in the presence of anything other than the beloved (Ekarativichikitsâ). In earthly love we see how often this Viraha comes. Again, when men are really and intensely in love with women or women with men, they feel a kind of natural annoyance in the presence of all those whom they do not love. Exactly the same state of impatience in regard to things that are not loved comes to the mind when Para-Bhakti holds sway over it; even to talk about things other than God becomes distasteful then. “Think of Him, think of Him alone, and give up all other vain words” अन्या वाचो विमुंचथ। — Those who talk of Him alone, the Bhakta finds to be friendly to him; while those who talk of anything else appear to him to be unfriendly. A still higher stage of love is reached when life itself is maintained for the sake of the one Ideal of Love, when life itself is considered beautiful and worth living only on account of that Love (तदर्थप्राणसंस्थानं) . Without it, such a life would not remain even for a moment. Life is sweet, because it thinks of the Beloved. Tadiyatâ (His-ness) comes when a man becomes perfect according to Bhakti — when he has become blessed, when he has attained God, when he has touched the feet of God, as it were. Then his whole nature is purified and completely changed. All his purpose in life then becomes fulfilled. Yet many such Bhaktas live on just to worship Him. That is the bliss, the only pleasure in life which they will not give up. “O king, such is the blessed quality of Hari that even those who have become satisfied with everything, all the knots of whose hearts have been cut asunder, even they love the Lord for love’s sake” — the Lord “Whom all the gods worship — all the lovers of liberation, and all the knowers of the Brahman” — यं सर्वे देवा नमन्ति मुमुक्षवो ब्रह्मवादिनश्चेति (Nri. Tap. Up.). Such is the power of love. When a man has forgotten himself altogether, and does not feel that anything belongs to him, then he acquires the state of Tadiyata; everything is sacred to him, because it belongs to the Beloved. Even in regard to earthly love, the lover thinks that everything belonging to his beloved is sacred and so dear to him. He loves even a piece of cloth belonging to the darling of his heart In the same way, when a person loves the Lord, the whole universe becomes dear to him, because it is all His.