Our calling, our life in Christ, begins when the Father directly interfaces with our mind for the purpose of revealing Himself, His ways, His purpose, His plan, His mind, His attitude, His perspective, His character, His love, His power, His mercy, His forgiveness, and on and on, that we might use our life and free-moral agency to choose life
But most important is that the Father Himself does this. God miraculously joins His own mind to ours! There is nothing mysterious about this at all. He begins to transfer His thoughts, His attitudes, His character—the Spirit of His mind—into our minds. When it tells us, "Grieve not the Spirit of God," he means, "Don't grieve the Father by resisting Him." He is transferring the invisible essence of His mind through the access that we have to Him by means of the death of Jesus Christ. He is by no means kidding about the importance of this process. He is helping us to understand that, even as we are influenced by those around us, unless we are in the presence of God, we will not be influenced by Him. This is why it is so vital for us to share life with Him.
This is where prayer and Bible study become important because we are literally in His presence and He can transfer the essence of His mind into ours. Nobody sees it. When we obey, we are giving Him permission to do this. We submit, using our free moral agency. There is nothing magical about this at all. It occurs when we respond to the influence of the interface that He creates between us when we believe His Word and submit, and when we strengthen the relationship through prayer, Bible study, and meditation.