While it is easy to think that happiness comes from being successful and having the money to buy the house/car/fabulous wardrobe you are lusting after, a 75-year-long Harvard study begs to differ.

In fact, key findings from the Grant Study, a 75-year-long Harvard research project on human development, says that the single most important aspect of happiness is positive relationships.

According to Waldinger, there are three key findings about relationships that predicted the overall happiness and health of the participants in the study.

The first is that loneliness kills. Yikes, how, you may ask? Well, according to the doctor, lonely people are less happy, and their brain functioning declines sooner than those who are not lonely.

The second is that the quality of relationships matters more than quantity.

"It turns out that living in the midst of conflict is really bad for our health," Waldinger said. "High-conflict marriages, for example, without much affection, turn out to be negative for our health, perhaps worse than getting divorced. And living in the midst of good, warm relationships is protective."

The third and final outcome is that good relationships protect the brain.

What the researchers discovered through the lengthy study was that when you are in a relationship where you can count on the other person, your memory stays sharper longer.

The moral of the story then? Seek out positive, healthy relationships and you'll live a longer, happier life.