Science of Identity Foundation:

So a person’s entire lifestyle can be dovetailed with his deep purpose in life. Such a person is the controller of his body, not a slave of his senses. Most people are servants of their senses and minds — they are godas (go means “senses”; das means “servant”). A bhakti yogi, however, strives to be a goswami (swami means “master,” and so goswami means “master of the senses”). A goswami is not dragged around by his senses, but instead uses his senses for his own desired purposes. Although goswami is also a title, in fact the real meaning of goswami is controller of the senses, whether one is externally with the title goswami, brahmachari, householder, or whatever.
Science of Identity Foundation – Siddhaswarupananda

The gist of the matter is that the Vaishnavas recognize distinction and variety in Brahman and the Mayavadis do not. The Mayavadi conception of the Absolute Truth is that God is impersonal and formless. Therefore, there is no room in their understanding for variegatedness, and as a result, they have to deny that the Supreme Brahman possesses energies or potencies. To admit energies or potencies would be to admit distinction; therefore, they reject this idea altogether. As a result, they cannot conceive of how individual sparks of Brahman, or individual souls, can exist. Their understanding of the shastric verses which describe Brahman as “changeless” leads them to conclude that various energies or spiritual sparks cannot be emanating from the Supreme Brahman. Let me put it this way: the Mayavadis more or less think that for the individual soul to exist, it would have to be a distinct piece of the Absolute Truth divided off from the rest of the Absolute Truth. And, therefore, the Absolute Truth would become diminished. This is a material concept, however. For example, if you take a piece off one of these books I’ve been reading, then the book will be reduced in size by exactly the proportions of the piece which has been taken off. If you take off enough pieces, then the book will cease to exist and what you will have left will be a bunch of separate, independent pieces. The Mayavadis view the question of individual souls like this. They think the Absolute Truth would have to undergo change or transformation in order for individual souls to exist. And what does this mean? This means, in the long run, that there will be no more Absolute Truth, since the Absolute Truth would have been divided into many pieces! Therefore, they reject the idea of individuality.