We all have that one fuck up, maybe more but we can start with the most memorable fuck up and what others can learn from it.
Mine comes with the message if you have a sump pump and you grow in the basement make sure that fucker is plugged in! What i learned always have fill on a timer when filling reservoirs, second plug that sump pump in! And just as back up you can purchase a water alarm for $15. And not go up to see if the pizza guy is there and space you left the hose on, went downstairs about 2 hours later to find about 6" of water in basement. Spent 2 hours shop vacn all the way into grow room only to find hose still on! Learn from my mistakes, if you tend to get a little blazed invest in the water alarm and a hose end timer.