I just wrote a book about this! It’s entitled Hearers and Doers: A Pastor’s Guide to Making Disciples through Scripture and Doctrine. I wrote it because your question raises a real problem: why self-professing Christians aren’t growing more like Christ.
I don’t have time to rehearse everything I do in the book here. But to answer your question speaking personally, I can say that what I desire above all is to be real before God. And, when I say “real,” I mean that I want to realize more fully what I truly am “in Christ.”
For me, the Bible and Christian doctrine are not simply about the true, but about the good and the beautiful as well – in a word, reality. Why has God brought me into being? To get real! That is, to become the creature he has intended humans to become, persons who can fellowship with him, enjoy his company, and glorify him in all that they do (in case you missed it, I just sneaked in the answer to the first question of the Westminster Shorter Catechism, which I suppose could also be my short answer to your question!).