Read Matthew 7:1-20.
Wow, this is surely a densely packed twenty verses! So much here about the spiritual journey. But the verses for me that simply ring true again and again and again in my life inside and outside of the church is this human capacity to see the speck in our neighbor's eye, while missing the beam in our own. I think that most people I know, including myself, could spend a lot of time in prayer on that one.
How often does an arrogant person complain of someone else's arrogance? A bossy person, about someone else being bossy? A withdrawn person about someone else being withdrawn...the list is long. The shrinks call it projection - denying certain unpleasant attributes in ourselves and placing them on someone else.
By whatever name one calls it - spiritual maturity, growing into the full stature of Christ, or just plain "growing up" - when we become more self-aware of the beams in our own eyes, the Reign of God is very near indeed.