What did the person do every day?

Now, I want to tell you a story about a strange person whose name was not known to us. In fact, no one cares about his name but his strange behavior. He always went to the same beer house at the same time every day and asked for two glasses of beer. Then he drank them himself. After that, he asked for another two glasses of beer and drank them the same way. One day the waitress in the beer house was so curious to hold her peace that she asked him, "Why do you always ask for two glasses of beer? Why not get one big glass instead?" The person smiled and answered, "Because I don’t like to drink alone. Two glasses mean that I drink with my friend. One glass is for me, and the other for him." But a few days later the person came in and asked only for one glass of beer. "Oh," said the waitress, "is there anything wrong with your friend? Has he died?" "Oh, no," said the person, "He is very well. This glass of beer is just for him. But I have stopped drinking beer. My doctor does not want me to drink any more because it is dangerous for me. "