When we are reborn spiritually, God himself—in the person of the Holy Spirit—takes up residence in us.
The fruit of the Spirit is the Biblical term for the group of divine attributes that God expresses in and through us as we walk in harmony with him.
These attributes are love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self-control.
Each person in the Trinity embodies these attributes in equal measure. In aggregate, their manifestation in us translates into true contentment.