I had that happen once. All this shitty vodka tasted like water and I knew I should've stopped but I didn't then I blacked out.
Or when you use it to lace pot/tobacco/meth/chew/anything you fricken want. Then you do whatever and get the PCP.
I found that my inability to limit alcohol consumption during a night of drinking often led to various negative consequences. Blackouts were a common occurrence. Ultimately, I quit drinking altogether, because I not only wanted to overcome my dependence on alcohol-induced loss of inhibition to participate confidently in social situations but also wanted to have a healthier lifestyle, which included more changes than my quitting drinking. Note that my experiences are just that--my experiences. I don't mean to suggest that any one else should avoid consuming alcohol; I only mean to share my personal experience on the matter.
Doom good for you! I'm glad you were able to do that. I think I'm headed down that path so I'm stopping early enough where it won't be that big of a problem... but only until the end of the year