. . you are doing it wrong.
A while back a federal task force met in Detroit to discuss violence and children. The findings were that pervasive violence has become a norm in some communities and when children grow up with violence as the norm it becomes easier to increase that level. Communities are destroyed. The task force went on to describe ways to counter that violence early.
The low-level negativity about people's lives is similar. In situations where people describe how they dread Mondays or their job or their family or how they are tired of the same ol' thing for lunch (when they pack it themselves).
The best counter to that attitude is to . . . . counter it. It's not about countering the comment (something I do and need to control better) but to counter the attitude. there are so many good things that happen every day in our lives. Talking about good things has it's own power.
Making today a good day is more than *not* saying anything when you can't think of something nice to say. Making today a good day is about going above and saying something nice.