This seventh Fruit of the Spirit is faithfulness. It speaks to our faithfulness to God and to each other. He grows this fruit in us when we are in relationship with Him. How do you do that? You seek Him sooner rather than later when you are facing a crisis; you give thanks to Him when you see how blessed you are; you talk to Him about all the little and big concerns on your heart.
In our everyday dealings, we need to be faithful to our values and to our commitments. Let your "yes" be your "yes" and your "no", your "no". Be a person of integrity. This is faithfulness to each other.
Faithfulness is a core characteristic of God. He will never leave or forsake His children. He wants a relationship.