Before anything else: God loves you all the time, even when you do something wrong. He doesn't love you because you're perfect, He loves you because you're His child, and that never changes.
Have you ever carried a really heavy backpack? After a while, your shoulders hurt and you just want to drop it on the ground. Telling a lie is like that, it's like putting a rock inside it. A lie seems small in the moment, but it weighs, and the worst part is it needs another rock to keep from falling, then another, and the weight on your back keeps getting bigger.
Whoever tells the truth walks light. They don't need to remember what they made up, don't get scared of someone finding out, don't need a new lie to hold up the old one. That's why the truth gives a nice peace inside, even when it's hard to say.
And when you've already put a rock in there, what do you do? The answer is beautiful and simple: just tell the truth. Tell God, and also tell dad, mom, or whoever you hurt. At first it gives you butterflies in your stomach, but as soon as you say it, the weight goes away and your heart feels light again. God never gets angry at whoever comes to tell the truth, He gets happy and gives a big, tight hug.