What is the most important thing about you? Or me, really?
What matters more than anything else?
A.W. Tozer, in his book Knowledge of the Holy, says this, "What comes into our minds when we think about God is the most important thing about us."
Reading the newspaper yesterday, I came across an advertisement promoting a controversial city policy whose headline began, "God does not exclude..." and I got upset, because that's wrong. Scripture is plain and clear that we are included into or excluded from God's family based solely on our faith in Jesus Christ. God does exclude.
This kind of thing is rampant, and I want you to know that it is vital to your spiritual health to have a good grasp of theology*. Anything you hear or read about God must be founded in scripture. You cannot believe in whatever you like and be a Christian. God is not always what you imagine him to be, so you must learn to adapt to God, instead of adapting God to you. If you don't, you are not worshiping God, you are worshiping a figment of your imagination. As Tozer says, "They that know thee not may call upon Thee as other than Thou art, and so worship not Thee but a creature of their own fancy..."
It's good to remember that God and his nature are not mysterious or unknowable--although at times, unfathomable. Who God is and what he is like are plainly and clearly revealed in scripture (which is why it's so important to read the Bible).
Now, it's important to ask where we learn theology. Everywhere. Really, most everyone I've met has an opinion about God. Your friends and family may or may not have Bible-based theology. The Christian books you read may or may not be theologically correct (and it's not always bad to read them, but you need to be responsible when you do). The songs you hear on the radio may be teaching you something contrary to scripture. Since the most important thing about you is what you believe about God, it only makes sense to filter these things.
Final thought: Be like the Bereans. Examine scripture to see if the message you're hearing is true, because knowing God and worshiping him rightly is the most important thing.
"Now the Berean Jews were of more noble character than those in Thessalonica, for they received the message with great eagerness and examined the Scriptures every day to see if what Paul said was true (Acts 17:11)."
*Theology is the study of the God. Your theology is what you believe about God.