Galatians 5:16 ... Walk in the (Holy) Spirit, and you shall not fulfill the lust of the flesh.
When we walk in the Spirit, the Holy Spirit, when we conduct our lives and do the things we need to do from the Spirit of God ... we will not be fulfilling ourselves, our fleshly wants and desires. Instead, we'll be choosing to do godly desires by our free will.
We struggle with this because of our flesh lusting against our spirit. Our new spiritual man has to grow in strength in order for us to overcome the things of the flesh and the mind, and for us to do the things that need to be done by the Spirit.
Reverend Robert W. & Mary C. Butler