NOTE: When you delete your keychain any saved password (i.e. passwords for wi-fi networks, websites, etc) WILL be removed and will have to be re-added when the new keychain is created.
To reset your keychain in macOS 10.9 to macOS 10.14 :
- Open Keychain Access, which is in the Utilities folder within the Applications folder.
- On the sidebar choose the keychain "login"
- Choose File -> Delete Keychain "login.
- Choose the option "Delete File and References"
- Quit Keychain Access
- Log out of the account
- Log back into the account
When you log back in a new Keychain will be created.