If someone hit your parked car, it doesn't matter that you were running late that day. If a tenant wrecked your apartment, it doesn't matter that he or she was a bad tenant. Tell the important part of the story insofar as a court would be concerned. A brief outline of a few key points about the nature of the claim. If you need help expressing your ideas, a great place to look is the Federal Rules of Civil Procedure, which has an official appendix of forms.
Defendant owes plaintiff the amount of said note and interest.
Complaint on an account billed but not paid for. Complaint for negligence. Work with an experienced lawyer in your state.