The mind (manas) is our deliberative faculty that makes us carefully weigh the pros and cons of several options before us. Buddhi is our discriminative faculty and the seat of the will, resolve, and conviction. Buddhi has to be cultivated through training and discipline, and by exercising the will in the right direction. The more decisive we are in small things, the more decisive we will be in greater things. Making decisions involves facing their consequences. That is why some people are indecisive. However, a spiritual seeker has to be decisive in all aspects of his life.
Sri Krishna describes a devotee dear to Him as "one whose mind and buddhi are dedicated to God." Dedication of mind to God involves cultivating faith in the divine Name, repeating it with devotion, singing the praises of God, and meditating on His form. Sri Ramanuja explains that dedicating the buddhi to God involves cultivating and strengthening the conviction that God alone is being propitiated by our activities; and when duly propitiated, grants us direct vision of the Self.
Dedicating one's mind and buddhi to God requires steadfast spiritual discipline. In the graded path of devotion outlined in the Bhagavad Gita (12.8-11), Sri Krishna assures us that a devotee whose mind and buddhi are fixed on Him is certain to live in Him from then on. If a devotee considers this discipline difficult, Sri Krishna asks him to take to the yoga of practice. Sri Ramakrishna illustrates the yoga of practice with an example:
"At Kamarpukur I have seen women of the carpenter families selling flattened rice. Let me tell you how alert they are while doing their business. The pestle of the husking-machine that flattens the paddy constantly falls into the hole of the mortar. The woman turns the paddy in the hole with one hand and with the other holds her baby on her lap as she nurses it. In the mean time the customers arrive. The machine goes on pounding the paddy, and she carries on her bargains with the customers....You see, she has all these things to do at the same time-nurse the baby, turn the paddy as the pestle pounds it, take the flattened rice out of the hole, and talk to the buyers. This is called the yoga of practice. Fifteen parts of her mind out of sixteen are fixed on the pestle of the husking-machine, lest it should pound her hand. With only one part of her mind she nurses the baby and talks to the buyers. Likewise, ... a householder should devote fifteen parts of his mind to God; otherwise, he will face ruin and fall into the clutches of Death. He should perform the duties of the world with only one part of his mind."
Sri Krishna offers an alternative to those who find the yoga of practice difficult: "Work for My sake; even by such actions you will attain perfection." For those not capable of following this, he offers a last option: "With a disciplined mind, offer the fruits of all your actions to Me."
A devotee with his mind and buddhi dedicated to God is described as sthira-matih, or "one who has strong and unwavering conviction about spiritual truths." He realizes that the essence of religion is the manifestation of his hidden divine nature. He has his mind fixed on the spiritual goal and is diligent and steadfast in his spiritual practice. He values doctrines, dogmas, rituals, books, temples, and forms as "but secondary details," in Swami Vivekananda's words, and understands that their main aim is character transformation and the unfolding of his divine Self.