In the philosophy of Aristotle, it seems like the soul is something of organizing principle. That is, you could claim Aristotle sees the soul as the foundation for what eventually becomes happiness.

According to Aristotle, “Pleasure is a state of soul.” Yet it seems like, in Aristotle’s mind, pleasure can become pleasant when someone loves what isn’t in conflict with their nature but what is in harmony with their nature. For Aristotle, the pleasant leads to virtue, which leads to happiness. As Aristotle himself says, “Happiness is an activity of soul in accordance with perfect virtue.”

As you might have noted, Aristotle seems to place considerable emphasis on harmony. His focus on harmony seems to lead to his distinctions between the continent person and the temperate person.

According to Aristotle, a temperate person will “have neither excessive nor bad appetites.” They don’t feel pleasure that opposes the harmony of their being. They are always, in a way, balanced.

The continent person, however, is susceptible to bad appetites. They appear to feel pleasure that might not be in harmony with their being. However, they have the ability to not be led around by this feeling of wayward pleasure.

As for differences and universality, you could say Aristotle allows for both because he acknowledges that people will interact with people differently depending on their identity. What benefits a wealthy person might not benefit a person of a lower class. There are differences. Those differences don’t mean you can act in a harmful way to some people. It means you have to make adjustments so that your conduct is beneficial to all people. The emphasis on conducting yourself in a way that helps all people could be considered rather universal.