Don't include everyone when you say "we have the capacity to go out of the Spirit into the flesh." At the beginning, no. Being filled with the Holy Spirit is an awesome experience, and we stay in the Spirit for as long as we can. That night for the first time in my life I saw a vision and heard God's voice. I still remember what He said. It was seared into me. Another thing that happened was I literally felt a dark heaviness lift out of my body. I now know it was the sin in my nature. We do not have 2 natures as some believe, we are like Adam was when he was first created without sin. He had free will. Even though we are not in the flesh, but in the Spirit, there are some fruit that may not have reached complete maturity. That is not going out of the Spirit, but is pictured in 1 John 1:7. While walking in the Spirit, any immature fruit that God hasn't completely matured in us, He will cleanse any trespass caused by them. This is why God tests us through our life to strengthen us. But eventually, our heart completely melts and we abide in Christ through thick and thin and "never stumble," 2 Peter 1:5-11. It takes almost a lifetime to get there, but God can perfect holiness in us, instead of just righteousness from when we were first born again of the Spirit and cannot sin against God's laws written on our conscience.
1 John 1:7
7 But if we walk in the light as He is in the light, we have fellowship with one another, and the blood of Jesus Christ His Son cleanses us from all sin.
2 Peter 1:10-11
10 Therefore, brethren, be even more diligent to make your call and election sure, for if you do these things you will never stumble; 11 for so an entrance will be supplied to you abundantly into the everlasting kingdom of our Lord and Savior Jesus Christ.