How can i do When Disk quota exceeded into Cpanel or WHM

The system failed to open the session file "var/cpanel/session/raw:***" because of an error : Disk quota exceeded at /usr/local/cpanel/Cpanel/session.pm line 268

1. Use : Download winscp (https://winscp.net/eng/download.php)
2. Install and connect your FTP account or WHM account then remove some files.
3. Finish!!!