It depends on where in the coping process they’re deployed. “It could be worse,” is used when the strong emotions of the situation pass and it’s time to move on. “Everything happens for a reason,” is used when someone is grappling to try to find meaning in whatever horrible thing happens to them. It’s easy for the mind to fall into senseless chaos, and these little proverbial sayings are there to provide gentle reminders that everything passes and life moves on, and you can too.
But you need to recognize what a person is needing at that point in time. Most of the time it’s just quiet support. You don’t offer up anything like this unless asked. You have no idea what they’re thinking at any given time. But they can be powerful if used properly.