“Be careful how you think; your life is shaped by your thoughts.” Proverbs 4:23 (GNT)

There are two common myths about what you believe. One of them is the sincerity myth; the other is the situational myth.

The sincerity myth says, “It doesn’t matter what you believe as long as you’re sincere.” But here’s the problem with that myth: You can be sincerely wrong. I’ve been sincerely wrong many, many times in my life. I imagine you have too. Sincerity is not enough. I can sincerely believe that the sun revolves around the earth. But it doesn’t matter how sincere I am about it—I’m sincerely wrong.  

The situational myth says it doesn’t really matter what you believe because everything depends on circumstances; you can believe one thing in one situation and believe another thing in another. That causes enormous amounts of stress in your life because it doesn’t make sense. Truth is always true.

It does matter what you believe, and it matters that your beliefs are consistent. The Bible gives three clear reasons why your beliefs matter.

1. Your beliefs shape your life. The Bible says, “Be careful how you think; your life is shaped by your thoughts” (Proverbs 4:23 GNT). Your beliefs determine your behavior. When you don’t know what you believe and why you believe it, your life ends up being shaped by beliefs you’re not even aware of. So if you want to change something in your life, start with your thoughts—with your beliefs. Change happens from the inside out. 

2. A faulty worldview causes all kinds of unnecessary problems in your life. The Message paraphrase says, “If people can’t see what God is doing, they stumble all over themselves; But when they attend to what he reveals, they are most blessed” (Proverbs 29:18). When you don’t know the purpose of life—when you’re building your life on the wrong set of beliefs—you just drift along, occasionally stumbling over yourself. But when you build your life on God’s truth—when you “attend to what he reveals”—you experience God’s blessings.

3. God wants you to share what you believe with other people. The Bible says, “Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect” (1 Peter 3:15 NIV). Our world needs people who know what they believe, know why they believe it, and know how to share those beliefs with others in love.

God made you in his own image—and for his purposes. And he wants you to build your life on beliefs that help you live those purposes to the fullest!