Why do things that make people feel more pleasurable end up causing greater harm to them?

Take mating and sexual activity as an example; it is an instinct for human reproduction and a normal physiological need.
But once it becomes excessive and uncontrollable, it can turn into an invisible killer that harms the body.
From a physiological perspective, mating and sexual activity stimulate the brain to release dopamine, which is what we commonly call the happiness hormone.