These violent delights have violent endsAnd in their triump die, like fire and powderWhich, as they kiss, consume

This quote means that when people do something that brings them great pleasure, it will also bring them great pain. It is like the reaction that happens when you mix gunpowder and fire. Together they make a powerful explosion that is both exciting and destructive. When the explosion is over, it creates nothing but destruction. In the same way, people’s reckless actions that bring them great pleasure can cause just as much damage in the end.