Attackers have become skilled at providing plausible reasons for viewing an attachment. First and foremost. Backup all of your important files. Verify that your backups contain the information you think they do. Have more than one copy of your backup archive.
Accidents happen, hardware fails, security measures are fallible.
Ensure that you have virus protection installed on your computer. Learn to use it, keep it up to date, and make sure that it functions as you expect. Use diskettes carefully. If your virus protection complains when you access the floppy drive, launch your virus disinfection program immediately. Do not open unsolicited email attachments.