Housekeeping is important: running out of disk space will mean system down. So doing housekeeping manually or by scripts frequently is recommended.
The file/directories which consume disk space and are growing are logfiles and core files.
You can most probably delete the core-filesin the directory:
Check with df -h before and after if it freed some substantial space.
You might want to move old logs to another server and/or delete old log files in:
The following command will list the directorie usage in MB, two directories down from the given one:
$ du -xm M --max-depth=2 /appgate | sort -rn | head -n 10
For more information regarding logging/syslog read the manual: