Take 5 is a bit of great advice coming from the STOPcyberbullying.org site

If you are targeted by a cyberbully:

• STOP!
  Don’t do anything. Take 5! to calm down.
• Block!
  Block the cyberbully or limit all communications to those on your buddy list.
• and Tell!
  Tell a trusted adult, you don’t have to face this alone.

Follow these great tips to help avoid future conflict with this person.