Before anything else: God loves you and looks at your heart with a lot of care. He never gives up on you, even when you mess up.
Grab a dish sponge and imagine something with me. If the sponge is full of clean water and someone squeezes it, what comes out? Clean water. And if it's full of dirty water, what comes out when someone squeezes it? Dirty water, right?
Notice something important: the sponge doesn't choose what comes out when it's squeezed. It just gives back what was already stored inside it.
Our heart is a lot like that sponge. During the day, we keep filling it up: with the things we see, with what we listen to, with the games and the way of the people we spend time with. All of that keeps getting stored inside.
Then the squeeze moment comes. Someone takes your toy without asking, you get startled, someone says something that hurts. And in that moment, out comes what was stored inside you. Jesus explained this in a beautiful way: the mouth speaks what the heart is full of.
That's why we take care of what goes in. It's not about being afraid, it's about choosing well: good stories, good music, people who tell the truth, a little time talking with God. That way, when the squeeze comes, what comes out is good.
And if something ugly comes out one day, you don't need to hide. Just ask God for help cleaning the sponge, because he's really good at that.