It is highly recommended you perform regular mySQL maintenance. You can do this by executing the following commands via SSH:
mysqlcheck --all-databases -r #repair
mysqlcheck --all-databases -a #analyze
mysqlcheck --all-databases -o #optimize
Repairing and optimizing mySQL databases goes a long ways to keep mySQL operating efficiently, and reducing the chances of mySQL crashing: which necessitates restarting the mySQL server (/etc/init.d/mysqld restart). Ideally you would create a cron job to automatically perfrom these actions at set times. For example, daily.