MATH PUZZLE: Can you replace...

There was this guy at a bar, just looking at his drink. He stays like that for half of an hour.
Then, this big trouble-making truck driver steps next to him, takes the drink from the guy, and just drinks it all down. The poor man starts crying. The truck driver says, "Come on man, I was just joking. Here, I'll buy you another drink. I just can't stand to see a man cry."
"No, it's not that. This day is the worst of my life. First, I fall asleep, and I go late to my office. My boss, outrageous, fires me. When I leave the building, to my car, I found out it was stolen. The police said that they can do nothing. I get a cab to return home, and when I leave it, I remember I left my wallet and credit cards there. The cab driver just drives away."
"I go home, and when I get there, I find my wife in bed with the gardener. I leave home, and come to this bar. And just when I was thinking about putting an end to my life, you show up and drink my poison."