Love—the kind of love that really makes a difference in this world—is more than just a feeling; it’s a choice. It’s a love that is committed to the loved one’s best interest. It’s a love that selflessly puts others’ needs first. It’s a love that chooses to know, listen to, and value the other person. And it’s a love that, according to the research discussed in this article, is the secret to happy relationships.

It’s also the kind of love that has kept Julio Cesar and Waldramina together for an impressive 79 years of marriage. And at 110 and 104 years old, respectively, that makes them officially the oldest married couple in the world. In their words, the key to the strength and stability of their relationships is simple: maturity, mutual respect, and, of course, love.