I don't think I'm an alcoholic but sometimes I drink at work because I'm stressed.
What is special about drinking at work?
It's a kind of a ritual, a belonging factor
Saying that drinking at work is a ritual is an excuse for doing something inappropriate. Drinking at work will get you fired someday.
It's my casual drinking and it's not going to affect my job performance.
Just because it's casual, doesn't mean that it belongs in the workplace. Your coworkers can see you, and might get influenced or tempted by what you are doing. Your work productivity matters a lot, so why not just wait until going home, it will be more rewarding!