Watching other people do worse than me motivates me to do even better in school. It really makes me happy.
Why would that make you happy?
I'm always such a nice guy but this is one dark thing that I really enjoy seeing.
It's great that you try hard in school and you should keep at it but getting joy out of watching your classmates fail isn't okay. Instead of basking in their failures as motivation try doing your best so you can also help them succeed. Offer to help people who need it and you'll probably feel even better.
You're asking me to help others so they'll get better grades?
Yes, imagine how happy you will feel when not only you succeed but the people that you have helped also succeed!