And do not grieve the Holy Spirit of God, with whom you were sealed for the day of redemption.This verse is a sort of interjection. It is a "Oh, and by the way... " verse, but it is also a "Don't forget, in all of these things..." verse. The Spirit of God was given to us as another Comforter, in place of an actual Christ walking this earth. He dwells within us, and according to this verse, you are sealed with Him, until the day of redemption.
I believe that Paul puts this verse in right here in the middle because we are to live by the Spirit. This list of examples is not to be a list of commands. They are examples of someone who is living by the Spirit. The word "grieve" means "to make sorrowful". As we commune with the Spirit of God, we are seeking to please God through the Spirit. It is important to remember that when we do the wrong things, He is affected. You can bring sadness to the Spirit of God.
That is why the key to change is not through human will power, it is a life through the Spirit, not our spirits, but the very Spirit of God. When we commune with this Holy Spirit, He is pleased with us, and we will be most delighted in Him.