Sadhana Bhakti Steps:
#4 - Be Singleminded
Singlemindedness is 'ananyata'. The literal meaning of this is keeping the mind and heart focused on only one. To have exclusive faith in Radha Krishna is what it means to be singleminded.
True affinity for Radha Krishna cannot develop in a dispersed mind that is dedicated to other forms of worship and meditation. It is only when the mind firmly settles on developing relational feelings with Radha Krishna that the true bliss of devotion can begin.
For example a laser is a coherent light source. All the light particles are in perfect alignment, moving in the same direction. Incoherent light is what is allowing you to read this page right now -- the light from any light fixture. The same photons are present in both kinds of light, but in coherent light they become so powerful they could cut through metal.
The mind is also extremely powerful and has a similar capacity to produce amazing transformations in you, but only if it is carefully focused. For this reason Rasik Saints have given this guideline to remain focused on one divine goal.
To support this idea, Veda Vyas has said in the Bhagwatam (4/31/14),
"When water is poured on the root of a tree, the water automatically reaches the branches, leaves, fruits and flowers of the tree. There is no need to water these parts individually. Similarly, when you adore and love Krishna, all other forms of God and all divine powers are automatically adored and loved, as Krishna is source of all the divine powers."
The mind is only one. When one subject resides in it, this is singlemindedness. In sadhana bhakti our mind should be filled with thoughts of and desire for Radha Krishna alone.