I can be so easily tempted to measure my own knowledge, growth, and journey in relation to other people. "Geez, why doesn't this person get it already?!" The problem with that kind of comparison, however, is that I rarely know the journey someone else has been on.
That's not to say that my own journey hasn't had its own twists and turns—it has. Because of that self-knowledge, I'm much more likely to give myself the benefit of the doubt. But when I refuse to give others that same benefit of the doubt, I'm playing a game of favorites and—surprise!—I'm the favorite.
Moreover, while the analogy of life as a journey is helpful, it's reductionistic because we are all on multiple journeys at once. I'm fairly advanced in my understanding of the Bible; but pretty behind in honestly expressing my emotions. I've developed a robust prayer life; but I'm pretty behind in experiencing empathy for others.
Jesus was on to something when he said we ought to consider the issues in our own lives as planks and the issues in someone else's life as specks. That's not to say we ought to never speak out against injustice and oppression; but if I only ever spend my energy looking at everyone else's problems but my own, I will soon become the very problem I'm upset about.