Before anything else: God loves you just as much on the day you're brave as on the day you're scared. His love doesn't grow when you're strong or shrink when you cry.
Do you know what a piggy bank is? The one where you put in one little coin today, another tomorrow, and it seems like it never fills up. But on the day you want to buy something special, you open the piggy bank and discover you saved up a lot, one coin at a time.
Courage works just like a piggy bank. Every time you do something good even when you don't feel like it, you put a little coin of courage inside. When you tell the truth even though you're scared to. When you say sorry even though it's hard. When you try again after making a mistake. Nobody sees those little coins going in, not even you. But they're there.
Then, when a really hard day comes, a big test, sadness, or fear, you open your piggy bank and you have courage saved up to spend. And if you feel like your piggy bank is still a little empty, don't worry, because there's an even better part: you can ask God for courage, and He lends you from His strength, which never runs out.