It seems there are two levels of friendship. One kind of friend accepts you as you are. This friend reaches out to you and makes no demands of change on your personality. Oftentimes, this will be a person you have known for a long time, such that you feel comfortable being who you are in your interactions with the other, though only to a point. Somehow, despite the mutual affirmation, there is a barrier that prevents the friendship from ever seeming full or round. This may not be due to a fault in either party; nevertheless, it remains the case that circumstances only allow them this type of connection.
On the other hand, the second level of friendship involves a stretching. While remaining very comfortable with this friend, at the same time you cannot remain static in your personality in order for the friendship to bear fruit. This does not mean that the friendship demands that you change who you are (that would make it no kind of friendship at all), but rather that the friendship does not allow you to grow complacent with yourself. In a way, your friend reaches out to you not simply where you are right now but also where you are going to be. This friend will accept your current state, and in fact accept it all the more deeply because of its orientation towards the future. At the same time, however, and without conscious effort, your friend encourages and challenges you to become a better and fuller you. Another aspect of this second kind of friendship is that the dynamism is mutual: one is not stretched more than another, but both grow in innumerable and complementary ways. Indeed, all friendship requires a growth in charity, yet the second kind sounds almost to the depths of the two friends' hearts. To use a common expression, the two "grow together"--and continue growing. The gift of this friendship is immeasurably valuable and necessary to us as we journey towards our true end.