Can only sympathise mate. When I was taking drugs daily, I done my absolute utmost to hide it from family and friends. Withdrawals, I would play off as the flu or a stomach bug. So try not to overthink that you didnt pick up on your best mates dependance on alcohol, as most addicts I've come accross it is there dirty little secret. Most will only come clean when they are finally done with their addicition. Repeating myself and rambling, but don't feel stupid about not noticing his addiction. Keep ploughing forward, next year is a new year