This was in Runescape, which I played when I was younger.
I was a young child. I was undertaking a quest to slay a dragon. The quest is one of the harder non-members quests, but I was a member. I had played the game for a long time and could easily complete the quest. I just never got around to doing it. One day, I finally decided to try completing it.
Before I continue, I should explain the death system in Runescape. When you die, it doesn't give you a second chance. You lose everything except your 3 most valuable items if you die. So obviously dying will really fuck you up as it takes a long time to replace the items you lost. Now this Dragon I had to kill was special. It's fire breath could kill you in one hit. regardless of your defense and HP. That's why you need a special shield to kill it. Now the shield is good against the dragon but piss weak against everything else. So while traveling to the dragon I had my superior shield equipped.
I entered the dragons chamber, charged at it with my long sword, only to fall dead in one hit. I had forgotten to equip the shield.
I don't need to explain what I did next.