In speaking of the nine character traits known as the fruit of the Spirit from Galatians 5:22-23, author Jerry Bridges says,
This is an awesome list of character traits to pursue, and our first reaction, if we are realistic at all, is probably to say, “I can’t work on all of these.” That is indeed true, if we were left to our own devices. But these traits are the fruit of the Spirit, the result of His work within us. This means not that we bear no responsibility for the development of Christian character but rather that we fulfill our responsibility under His direction and by His enablement.
The fruit of the Spirit is a mark of a supernaturally changed heart and by studying each of the listed virtues we can understand what it means to develop such a heart - to grow in Christlike character.