These two words are vital, literally. That is the word vital is a part of the Greek definitions of both words. These two words are at the core of what we know as life beyond are biological existence.
I accept these words as distinct but inseparable by human understanding. I base this on the word of the Lord Jesus. We must be born a second time of spirit, hence the phrase "born again." I think that being born of the spirit marks the beginning of our intimate relationship in spirit with God. I cannot argue effectively from the scripture there was no spirit in a person before being born of the spirit, but I think that is the case. Even if that is not true, being born of the spirit must mark the start of something new based on spirit. This event marks the divide between soul and spirit.
I accept the soul is the vital force that is our eternal being. It is known by us as we experience our thoughts and feelings. These two, mind and heart, are a function of the soul. The soul is tied to the body. The body holds the soul temporarily during this life. The soul embraces spirit to draw upon the life therein.
The Holy Spirit is a like a wind. The soul is so structured that it needs "spirit" to be full of life. The soul is born of the Spirit of God or it remains attached to the only other spirit-like entity that exists, the spirit of the anti-Christ. These two opposed spirits are all there is to animate the soul fully.