The development of personality occurs in phases throughout life. For someone who is young, the main task is to develop use of their preferred mental functions. As one matures, however, and approaches midlife, there is often a need to develop greater comfort with using your non-preferences. This can help you increase your performance at work, and increase your ability to deal with different people and circumstances.
As with all types, an INFJ can achieve personal growth by developing those functions that are not fully developed, through actions such as involving others in the development of one's own personal vision or goals, investigating and collating hard facts/data, and learning how to plan and control projects. It is the area of logistics that presents the greatest challenge, and potential for growth, for that doesn't depend on people's growth or development and it requires taking a more objective approach than is natural for an INFJ.
A common theme of development for all types after midlife is individuation. This involves learning to value and develop various "opposites", not just the opposite typological preferences. Through reconciling opposites, your personality becomes more individual and unique, and your personality type may change. You might also reach the stage where your closest personality type is no longer a description of you, but it is merely a part of your personal history.
Next: INFJ and Stress