"Pleasant it is, when over a great sea the winds trouble the waters, to gaze from shore upon another's great tribulation; not because any man's troubles are a delectable joy, but because to perceive you are free of them yourself is pleasant"

In this quote, Lucretius is describing the sensation of relief and happiness that originates from observing another person's bad luck from a safe distance. He is not recommending that people get a kick out of the suffering of others, but rather that it can be reassuring to realize that one is not going through the exact same difficulties as someone else. The image of enjoying troubled waters from a tranquil shore reinforces this contrast between chaos and calm, and suggests that a specific range is essential to totally appreciate the freedom from difficulty enjoyed by an observer in such a circumstance.