A becoming need
We become what we love. Therefore, we need to read the Bible.
The angle I'm playing here is this: By temperament, a Christian is likely to find different aspects of the Faith more appealing than other aspects. There are "Christmas people," and "Good Friday people," and "Easter people."
That's all right and fine; such diversity gives glory to the God Who gave us Christmas and Good Friday and Easter.
What's less right and fine is for me to become, say, a Christmas-without-Good-Friday person. That can happen if I love Christmas too much. Or even if I love the Incarnate Jesus "too much," which I could do by, for example, loving the mystery of His Incarnation in an abstract way isolated from the death and resurrection that were the goal of the Incarnation. (To [try to] be clear, I don't mean we can love Jesus too much, I mean we can love the dogma of His Incarnation too much.)
What's needed, in a word, is balance. We need to balance our natural temperaments with the fullness of God's revelation; hence we need to read the Bible. (More generally, we need to know Revelation.) The longer I go without reading the Bible, the more I am going to form myself based on whatever happens to be in my head. That, naturally (using that word in a very strict and literal sense), will be an imbalanced image of the Person of Jesus. If I love an imbalanced image of Jesus, then it isn't Jesus Himself that I love, and it won't be His co-heir that I become by my love.
Reading the Bible, maintaining that direct contact with the Holy Spirit Who gives life to the words of Scripture, will help me obtain the grace needed to perfect my natural inclination to think of the Faith in terms of, say, babies and joy. I'll still think of the Faith principally in terms of babies and joy, but within in the context of the full Gospel.