Our pride keeps us blind to our own faults and immature. It is only through seeing our own weaknesses and correcting them that we start to grow towards maturity. An immature person will get angry if you call her immature, and yet that very anger is a strong indicater of her immaturity. Compare the response of a more mature person. When you point a character defect of a maturing person, she will be thankful and will begin correcting it.
The truth is that we all are immature in one way or another. Maturity is not static horizontal line. We don't mature evenly in all areas at the same tims
Instead, our maturity could be viewed as as Variable Maturity level chart.
Some levels we may be (seemingly) vey mature in, and in other areas we may be very immuture in.
Any areas that we get angry about, refuse to change, or are blind to are areas in our life that we stay immature in.
The virtues are the areas that help us to mature. As we improve in each of the virtures, we become more mature. Conversely, if we stay selfish, angry, etc., we stay or become more immature.