Question: What is the form of exclusive and unswerving devotion?
Swamiji: Exclusive devotion is when there is no second entity. There is nothing else in the world. There is no other. There is no other who is not yours. There being 'no other' can mean (i) there is only God and it also means (ii) everyone is mine (there is no 'other'). You do not see anyone or anything else. This is true love. There is no one who is 'other'. No second entity. Like the chaste wife does not even accept the existence of a second male. There is only one male for her - her husband. Similarly in exclusive devotion there is only God. All that is seen is only prakriti (nature). There is no second entity and that entity is mine.
Source: "Art of Living" by Swami Ramsukhdasji