If someone has made you fell sad and upset you will know if someone has been saying mean words or you have been kicked or punched.
Here are some ways to stand up to that person.
If they have been making you sad a lot that you are having lots of problems, you can always ignore them or if you have tired that and they are still making you sad you can go to a peer mediator or talk to your mum and dad or your teacher about it.
You can always tell the person about how you fell and ask them why are they making you sad because you never know why they are doing it.
If you make someone sad stop and think to yourself are you hurting their feelings and would you like to be sad like them.