It is by the Word of God. It is the Word of God that separates between the spirit, soul and body. The Word of God builds our spirit and we grow and gain understanding about the spirit realm and become more spiritually in tune with the spirit realm so that we are able to see into that realm and hear in that realm and feel in that realm just as Jesus did when He walked on the earth as a man anointed by the Holy Spirit.
Heb 4:12 For the word of God is living and powerful, and sharper than any two-edged sword, piercing even to the division of soul and spirit, and of joints and marrow, and is a discerner of the thoughts and intents of the heart. NKJV
Because our emotions change and fluctuate they can easily betray us, our thoughts unruly can lead us to self-destruction, our urges for self-gratification obscure our ability to hear from God; so the Lord is calling us to come out of living out of the soul realm and instead live out of our spirits for they are eternally fused with the Lord and His Kingdom. We can't hear the voice of the Lord unless we listen with the ears of our spirit.