If you ever make your own logs, rotating them is easy. One way is to use logrotate. For example, I have daily mirror logs dumped in /var/log/mirrorme.log and /var/log/mirrorme-error.log, so I make a new file in /etc/logrotate.d/, call it whatever, and put something like this in it:
logrotate is run daily from /etc/cron.daily, so this setup mails me the log and zeroes it daily. You can see man logrotate and whatever you have in /etc/logrotate.d/ for more examples.