When I was your age, I came home one day from school and told my dad about the funniest thing that happened that day — something that involved a group of kids playing a prank on an unpopular girl in my class.

Granddad was not amused. In fact, he was angry with me. He told me, in no uncertain terms, that the prank was not funny. He reminded me of his brother, my uncle, who had struggled his entire school life with bullies and teasing. I had never seen Granddad so angry with me before. I even saw a tear roll down his cheek when he made me swear I would never do anything like that again. “But it wasn’t me,” I protested. “I just watched.” He put his hands on my shoulders and looked me in my eyes. “That’s the same thing,” he said. “It’s the same thing.” That’s still the only time I have ever seen Granddad cry.

When I was growing up, we didn’t have the Internet. There were bullies and kids who picked on others like the kids in my sixth grade class who pulled that prank, but just about everything happened at school, in person, or on the phone. By the next day, it was all but forgotten by most of us, for the most part. We didn’t have social media sites like Twitter or Tumblr or Ask.fm. If we took pictures of ourselves, we had to actually print them out at CVS. We couldn’t post them immediately on Instagram. In your world, everything moves much faster than it did for me. There’s so much more room to make a bad choice, and those bad choices don’t go away so easily. It’s overwhelming to me, so I can only imagine how it feels to you. Everything you do or say can be instantly posted for all the world to see. Don’t be fooled — everything you post on online is forever.

But for as much as the world has changed, one thing has stayed the same: As your Granddad once told me, whether you are the one picking on someone else or the one watching it happen, it’s the same thing. And it’s all wrong.

You are all wonderful people whom I am proud to call my children. You fight with each other way more than I would like, but some of that is to be expected. I think you have learned by living and fighting with your siblings that words can hurt as much as fists. A lot of the time, it’s what you say to each other that wounds the deepest when you argue. The same is true for your interactions with the rest of the world: words can hurt.

Please remember the potential words possess as you walk through the world and interact with your peers. Your words are powerful, so choose them carefully. Your words will last, so make good choices when you choose to put them on the Internet. Remember that your words include “likes” on Instagram and Facebook and Twitter. If you “like” something that hurts someone else, as Granddad said, it’s the same thing as if you wrote it yourself.

Words can hurt. On the other hand, words can heal too. If you use your voice to say, “This is not okay,” or “Cut it out,” or “I’m not cool with this,” you can make a difference. Because while I think it is the right thing to do to be kind to everyone you meet, I think that true kindness — true GREATNESS — takes the courage to say, “This is wrong.” That’s the kind of courage that heroes have. That’s the kind of courage I hope you will have.

I want you to use your words. I want you to use them to defend yourself if you have to, or to let me know if you need me or if you need help. I want you to use them to defend others who need them, or to let me know if others need help. We are a team here. You don’t have to do it alone. But your words are the key to everything. Every single face you see at school belongs to a person — a person with a family, a person with dreams, a person who has good days and bad. Be kinder than you have to be; use your words carefully and for good. I’m here if you need me, and I love you more than anything else in the world. I believe in you.