OPTIMIST: "HALF FULL!"; PESSIMIST: "HALF EMPTY."; MATHEMATICIAN: "ACTUALLY, IT'S 499/1000 FULL AND 501/1000 EMPTY."; INTERNET: "IF YOU EXPRESS YOUR OPINION ON THIS GLASS, I WILL RELENTLESSLY CRITICIZE YOU FOR EVERYTHING YOU DO."; MECHANIC: ''THE GLASS IS TOO BIG''