True, it's not a great example-- I honestly think the author has missed the point of the exercise. "We might be down for thirty minutes" is not actually that bad of a thing, as you point out; he's just practicing avoidance, which is not the path to happiness.

However, Buddhist mindfulness really does predict that the only way to be happy is to contemplate, and accept, your most secret and horrific fears. Try, "No matter how hard I work, what I make will eventually fail and be replaced." Or maybe "Everyone and everything I love will die and be utterly forgotten in a few hundred years."

This is, in fact, practicing happiness. It seems absurd, but if you can't be happy and productive while accepting these thoughts, you weren't ever really happy; just in denial.