You’re in checkout line at a store, someone says, “This is the worst day ever!” How do you lighten the mood?

You're in the checkout line at a store, and someone says, "This is the worst day ever!" How do you lighten the mood? I am always curious about the feedback in this question. Some will try super hard to manage the person's feelings, and that's because that is what they would want someone to do. Others will let them be and not bring light to the statement, for that is what they would do. I would probably try to lighten the mood by making a joke or finding something positive to focus on in the situation, because that's what I would want.
This is a great example of us humans always thinking about ourselves, it's not good, bad, wrong or right, it's how we are. We project outward what we want. What if we got curious and asked what it is that they need?
By the way there's no right way to handle this, it's just a conversation starter, a mind shift in seeing that we all have our wants, needs, and desires, what if we stopped and considered what other people want?