Things one should never do
Linux was new and all the rage and I'd just come back from some sort of system administrator training, likely an IBM AIX class. I was liking the whole Linux and UNIX thing and was having a grand old time setting systems up. More than that, though, I was a badass. I could make the system jump, roll over and lie down all with the power of my little finger. This too was in the days of limited disk space and the need to partition file systems for better performance. One night, sometime after midnight, I got this bright idea to make all the file systems separate partitions. It wasn't enough that /usr and /usr/local had their own. After all if two file systems could be mounted on separate disks then why not more things went OK while I moved /home and /opt. On a roll I moved /etc to its own partition. Having carefully copied /etc to the partition and had everything setup it was good to go. Mounted it and everything was good. Well until the next reboot that was. As it turns out it is rather challenging to find the mnt file to know which partitions to mount when it's not mounted as a part of the root filesystem.
It took a while to recover from that one but you can bet it is one "trick" I won't try again.