Jessie Penn-Lewis emphasizes the critical distinction between the soul and spirit as outlined in Hebrews 4:12, illustrating how the Word of God acts as a sharp sword to divide these two aspects of our being. She explains that believers must yield to Christ, our High Priest, who discerns the thoughts and intents of the heart, enabling us to live spiritually rather than soulishly. The process involves surrendering our entire being, engaging in persistent prayer, and taking up our cross daily to allow the Spirit of God to work within us. By cooperating with the Holy Spirit, believers can experience a transformation that aligns their soul with the spirit, leading to a life that reflects Christ's love and purpose. Ultimately, this journey requires a commitment to discern and separate the soulish influences from the spiritual life empowered by Christ.