I researched the topic about the relationship between body, soul and spirit and found some interesting articles. Let me summarize the key points of these articles as follows.
Body is our fleshly-self and it has a lot of worldly needs, like hunger, competition for resources, lust, and selfishness. Soul is the mind, will power and emotions, which is the gateway to the spirit. Spirit is our innermost being, which lies in our subconsciousness and controls a lot of our emotional reactions and behaviors. Before we surrender our will to God, our souls are in the wilderness and we are not aware of how sins affect our lives. However, when we start to communicate with Him and repent for our sins, our spirits will connect with the Holy Spirit and we will gradually gain wisdom from Him. Then if people keep praying, they will be able to submit their body, soul and spirit under the will of God.