Sometimes when I’m worried, I feel like a fog of fear and anxiety is swirling all around me, blocking out the ability to think clearly and trust God. It quickly fuels responses like complaining, grumbling, being self absorbed and selfish, or making a quick decision that isn’t led by God. 
As I begin to worry, I remember that I’m a Christian and I’m not supposed to worry. So my defense mechanisms kick in. I reason:
I’m not worried, I’m just thinking
I’m not worried, I’m just wondering!
I’m not worried, I’m just concerned!
I’m not worried, I’m just mulling over a problem!
I’m not worried, I’m just a little bothered!
But then honesty rears its unwelcome head, and I surrender. 
OK! I’m worried!
I’ve gone through this scenario many times. It’s so easy to deceive myself into thinking I’m not worried—I’m just thinking too much! Besides, don’t I need to plan just in case something terrible happens? But at a certain point, thinking, wondering, being concerned, mulling, or being bothered becomes worry! And at that point, I’m not trusting God with my whole heart. 
Now, there is indeed a difference between fear, careful thought and worry. Fear can be a legitimate emotion which is God’s warning signal to do something—QUICK! (As in, that bear coming towards you looks really hungry!) Fear can turn into worry if we (a) don’t take action (like scream or play dead!) or (b) release control because we have no power over the situation or person (that doesn’t apply to the bear analogy!).
Fear in itself is not sinful when it’s based in something legitimately dangerous. If your daughter is late getting home from a date, you might feel fearful and it is based on something legitimate. But it doesn’t have to turn to worry as you pray for her safety.
Careful thought is what our mind does when faced with an uncertain situation or problem. That’s to be expected. God wants us to use the mind He’s given us.
But as we try to figure out the solution, our careful reasoning can easily slide into worry if we don’t turn our attention to God, ask for His input and trust Him. 
One question I ask when I speak on the topic of worry is: “How quickly can your ‘thinking’ become ‘worrying’?” In other words, how long do you spend thinking or mulling over something before it can become worry? The record answer from women in my audiences is “five minutes.”
Here’s an assignment: Pay attention to how quickly your “thinking” becomes “worrying.” You might be surprised that sometimes it’s only five seconds!
And then ask yourself, “What does my worry say about who God is?”