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, INFPs can achieve personal growth by developing all functions that are not fully developed, through actions such as developing plans, organising your work area and, when making important decisions, listing options and including a formal cost benefit analysis. You may also need to be more open about your personal values, and pay more attention to the current problems that need solving. You could perhaps learn to enjoy the present more, rather than always working towards a better future.
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: INFP and Stress