I think hitting "your bottom" is when you finally get that crystal clear realisation that you can't carry on doing what you're doing anymore......like Gracie said I think it can be emotional or physical. For a lot of people it is probably the day the doctor says "this WILL kill you if you carry on," could be the day your wife leaves or you're told you can't see your kids any more......I think the bottom is just that final dawning that its all f*cked and you've got no choice but to start to try and claw you're way back to real life or only oblivion is left to look forward to.