This is a great question! People sin because of something called our "sinful nature." When Adam and Eve disobeyed God in the Garden of Eden, sin entered the world. Ever since then, every person has been born with a tendency to sin.

Think about it—nobody had to teach you how to be selfish or tell a lie. Those things came naturally! That's because sin is part of our nature as humans.

We also sin because we're tempted. The devil tries to make bad things look good, and sometimes we give in. Even when we know something is wrong, we might still want to do it.

But here's the hope: Jesus came to give us a new nature! When we believe in Him, the Holy Spirit comes to live in us and helps us want to do good instead of bad. We'll still mess up sometimes, but God is always ready to forgive us and help us do better.