An 85-year Harvard study discovered that the most important thing that brings us happiness in life is positive relationships, and your friendships are a huge component.

Maintaining long-term friendships that are stable is one of the seven practices of people who live to be happy and healthy, the study found.

Yet, each of our friendships can look different, and it turns out that your friendships shouldn’t all look the same.

The renowned Greek philosopher Aristotle narrowed down three types of friendships that we all have. And Arthur Brooks, a Harvard professor who teaches a course about how to manage happiness, believes we need all three friendships to truly feel happy in life.

These are the three types of friendships, according to Aristotle, that appeared in Brooks’ article titled “The Best Friends Can Do Nothing for You” which he shared in the Harvard happiness course:

1. Utility friendships: “Think about the relationships you have with people with whom you work, or with whom you do business. These relationships tend to be transactional in nature,” wrote Brooks.
2. Friendships based on pleasure: “This type of relationship is based on mutual admiration because each person draws pleasure from the other. If a person finds their friend funny, interesting, and a source of enjoyment, it is likely a friendship of pleasure,” Brooks wrote in his article.
3. “Perfect” friendships: “By Aristotle’s standards, perfect friendships are those between people who have a mutual love for something that not only brings them together, but elevates their behavior to virtue. A relationship is perfect not when it is based on utility or pleasure, but when it is focused on improving the circumstance of the other person,” Brooks notes.

Utility friendships aren’t always the most satisfying, and pleasure friendships may not deepen beyond shared interests — but both are important.

These two kinds of friendships are useful for advancing in life, “but they don’t usually bring lasting joy and comfort,” Brooks wrote. While we need utility and pleasure friendships, “we can’t afford to risk these connections through confrontation, difficult conversations, or intimacy,” says Brooks.

For this reason, “perfect” friendships are extremely necessary to have in life, in addition to the other two types of friendships, for true satisfaction.

“You might not be able to put it into words, but you probably know how these ‘perfect’ friendships feel,” Brooks wrote.

“They often feature a shared love for something outside either of you, whether that thing be transcendental (like religion) or just fun (like baseball), but they don’t depend on work, or money, or ambition.”

CNBC