Spiritual maturity begins with basics, but moves on to deeper understanding. It's in the Bible, Hebrews 6:1, TLB. "Let us stop going over the same old ground again and again, always teaching those first lessons about Christ. Let us go on instead to other things and become mature in our understanding, as strong Christians ought to be. Surely we don't need to speak further about the foolishness of trying to be saved by being good, or about the necessity of faith in God."
Spiritual maturity is a process that takes time and leaves our own desires behind. It's in the Bible, I Corinthians 3:1-4, TLB. "Dear brothers, I have been talking to you as though you were still just babies in the Christian life, who are not following the Lord, but your own desires; I cannot talk to you as I would to healthy Christians, who are filled with the Spirit. I have had to feed you with milk and not with solid food, because you couldn't digest anything stronger. And even now you still have to be fed on milk. For you are still only baby Christians, controlled by your own desires, not God's. When you are jealous of one another and divide up into quarreling groups, doesn't that prove you are still babies, wanting your own way? In fact, you are acting like people who don't belong to the Lord at all. There you are, quarreling about whether I am greater than Apollos, and dividing the church. Doesn't this show how little you have grown in the Lord?"
Spiritual maturity puts away childish things. It's in the Bible, I Corinthians 13:11, NIV. "When I was a child, I talked like a child, I thought like a child, I reasoned like a child. When I became a man, I put childish ways behind me."