Mind is a powerful agent from the lower Spiritual Lord. It keeps company with the Soul both in the body and up in the lower Heavens. It has been keeping the Soul enslaved for its own purpose because Soul gives life to organs and Mind enjoys them. From this arises the cause of action, and from action arises the cause of suffering and enjoyment. Lust, Anger, Greed, Love and Determination are its principal powers. If these powers are not misused, and the Mind is made to enjoy the spiritual bliss of the NAME and Heavens, it is a source of the greatest help to the Soul to getting salvation. As long as the Mind is wavering and restless and until it realizes the degradation to which it has fallen from the Heavens and turns from the wrong and downward path, there is no power on earth that can do any permanent good to Soul. Hence the necessity of the good and pious company (externally and in meditation) of the Mediator, Satguru, Murshid or Pir.
Guru Nanak says: "Remove the restlessness of the Mind, take instructions from Satguru and reach the Kingdom of God immediately."
I.E. if you wish to unite with the Beloved, associate your Mind with your Soul. Unless the Mind is obedient to Soul, the wounded heart will not find the remedy.
In the higher stages Mind becomes slave of the Soul and works as a faithful attendant. When Soul leaves the body for the highest Heavens in the end, the Mind reaches the heaven of its origin and stays there permanently.
A steady and concentrated Mind is necessary both for spiritual and temporal success. Mind is likened to mercury, as it is restless by nature. Some Saints liken it to a monkey. As the army of monkeys helped Ram Chander to win back his lost Sita, so can we obtain spiritual perfection by concentration of the forces of Mind.