In pairs/threes or around the class students have a conversation alternating between Fortunately and Unfortunately.
Teacher can provide a first sentence to begin
(e.g. Fortunately I had no homework today.)
Next student says something unfortunate
(e.g. Unfortunately, my mum made me study anyway).
Next student states a fortunate event
(e.g., Fortunately, I was studying on the computer so I could go on Facebook)
and so on..