Very true, I didn't learn until I rented my own place at 20 and started paying my own bills. I found myself going round my mum's and turning HER lights off...and my sisters...and my girlfriend's mum's...and anyone else's house I go into for that matter
but right now I've got a 800watt heater in the attic trying to dry out the ceiling after I knocked a pipe off the boiler and water has gone everywhere! my own house i'll add so no insurance claim, unless the ceiling falls through in which I'll just repair myself.