Worst mistake I ever made, beside of course the night when we left a fully loaded automatic rifle on the roof of our van, was a move from Tomcat + JDBC to JBoss + Hibernate. It went from fast (JDBC) and stable (Tomcat), to unstable (JBoss) and slow (Hibernate).
It was that period in my life with involuntary dealings with guns and ammo, called the military. I was commander of a security detail and we often went about in our region with our gear and live ammo.
This particular night we had our last stop at about 4AM and went back to base. At base it appeared the UZI belonging to the driver was missing. Headlines like "Boy finds military weapon and empties it at the gas station" is a certain ticket for jail time, so I made sure my concerns resonated with the team. Luckily the driver remembered leaving the UZI on the roof, so we went back to exactly the last spot and spend a good hour searching in that neighbourhood.
I think it was then about 6AM and it was getting light. We were getting desperate and I called another commander to assemble his team to help searching. At that point I figured why not replay the whole event with another gun? And so it happened: when that fell off the roof, it landed just a few meters from the UZI.
