linux + find command with rm -rf

why the following command removed the tmp directory under /var and how to avoid this?

  find /var/tmp -type d   -ctime -1  -exec rm -rf {} \;


pwd
/var/tmp
[root@linux /var/tmp]# find /var/tmp -type d -ctime -1 -exec rm -rf {} \;
find: /var/tmp: No such file or directory