It happens, usually with those who drink a lot. As we age, we face and handle stresses differently. In our 20s, most of us feel immortal and unstoppable. By 30, most of us realize we are not. So, the cheery, drunken attitude can suffer for booze is an uninhibitor, which means we might spew forth a lot of stuff that irritates, angers or we fear that normally we would keep to ourselves.
By the time I hit 35, it was noticed by friends that when smashed, I was often no fun, belligerent, often apt to detonate at the slightest trigger or sullen. I had to cut my drinking way down and even today, might get happy, but never smashed. Plus, I noticed in myself and have heard from other drinkers that as they aged, they know within a drink or two if they are going to have fun or not. If not, then they make the drinks last or stop drinking.
Plus, by 30, the body has changed, has begun to slow down, accumulate bits of damage from idiot stunts when 20, reflexes drop a bit and emotional out look often alters. At 25 one could drink all night, get up after an hours sleep, go to work, feel bad, but put in a days worth on the job, get off work feeling OK, and go out and party a bit that night. At 35, often one awakens with the hangover and feel like they’re about to die. They’ll skip work or not do a real good job and might feel like crap by days end and might prefer to sleep afterwards instead of going out.
Changes in the body.
Plus, real heavy drunks destroy brain cells. That effect accumulates over the years and can change the drunken personality.