"Theology is learning to think well of God."
I'm not sure who first said that, but theology as learning to think well of God captures the heart of its intentions. In the early church, Augustine shared a similar sentiment: "To think the best of God is the truest foundation of piety." Theology is supposed to drive everything else in the Christian life, but sadly, theology is a sort of buzzword for the problematic, impractical and unnecessary part of the Christian life for many believers today. It's seen as the thing that causes division, contention, and strife among believers, or something only scholars and professors care about. Many Christians avoid it altogether because they just don’t have the time for it, or because they think it's hard to understand. But the problem with our modern and popular neglect of theology is that everyone is already doing theology whether they know it or not.
Theology is the study of God. Everyone believes something about God whether correct or not, whether positive or not, and live their lives and see the world through the influence of it. But theology is much more than just thinking about God. It is how we think about ethics, practical Christian living, how-to advice, and our psychological makeup. The problem is we don't realize how much of an influence our thoughts about God play in how we think about everything else, and because we don't put much emphasis on our thoughts about God, everything else is disordered and misaligned.
When we think about those practical parts of life without thinking much about God, it is still theology, but it is bad theology. Bad theology is when our learning and teaching stop at us. That's what happens when we talk about God, the gospel of Jesus, the Holy Spirit, salvation, or the church, but the focus is on our interaction with each of the subjects: how God relates to us, what the gospel means for us, what Jesus did for us, what the Holy Spirit does in and for us, what the church can do for us etc. In other words, we care about how theology applies to us without much consideration for the theology itself.
Good theology understands application is good and necessary, but without properly understanding theology, we soon have no substance to apply. Theology, then, is more than simply studying God, it is studying God as He is in Himself and for Himself; it is thinking for the purpose of understanding everything in the world around us, including ourselves from God’s perspective.
I like pastor and author Albert Martin's insight into how theology influences the Christian life, and I think it helps us 'regular Christians' see the value of theology. He writes,
"The end for which God gave his truth was not so much for the instruction of our minds as the transformation of our lives. But as a person cannot come directly to the [Christian] life and experience, he must come mediately through the mind. And so God's truth is addressed to the understanding and the Spirit of God operates in the understanding as the Spirit of wisdom and knowledge. He does not illuminate the mind simply that the file drawers of the mental study may be crammed full of information. The end for which God instructs the mind is that he might transform the life."
The life of the Christian is tied directly to the life of their mind. If they do not grow in wisdom and understanding, they will not grow in godliness. If they do not grow in their knowledge of God, they will not grow in their love for Him. Paul says much the same by way of inference in the way he prays for the Christians in the various churches.
"…I make mention of you, always in my prayers making request, if perhaps now at last by the will of God I may succeed in coming to you. For I long to see you so that I may impart some spiritual gift to you…that I may be encouraged together with you while among you, each of us by the other's faith…So, for my part I am eager to preach the gospel to you also who are in Rome" (Romans 1:9-15).
"[I] do not cease giving thanks for you, while making mention of you in my prayers; that the God of our Lord Jesus Christ, the Father of glory, may give to you the spirit of wisdom and of revelation in the knowledge of Him" (Ephesians 1:16-17).
"And this I pray, that your love may abound still more and more in real knowledge and all discernment, so that you may approve the things that are excellent, in order to be sincere and blameless until the day of Christ" (Philippians 1:9-10).
"For this reason also, since the day we heard of it, we have not ceased to pray for you and to ask that you may be filled with the knowledge of His will in all spiritual wisdom and understanding, so that you will walk in a manner worthy of the Lord, to please Him in all respects, bearing fruit in every good work and increasing in the knowledge of God" (Colossians 1:9-10).
Do you see the theme? Knowledge of God (theology) leads to godliness. That means theology is for regular Christians because it is what regular Christians need to fuel a life of godliness.