This is a good exercise in looking at things from a different perspective. Give the students an example such as the one below, which is a common saying in England.
Divide students into pairs or teams. One side starts with a positive statement e.g. The good news is that I won a million pounds. The other team/partner responds by turning it into a negative. See how long they can keep it going.
Language Focus: Connectors of contrast.
This can be a nice warmer before planning an argumentative essay.