I once saw a quote that really pinpointed the way I feel about my friends, “Your friends are family that you choose”. I have long said that your friends are people that you choose to hang out with and family are people you have to hang out with. I am not saying that family is not important, they are extremely important, but you make the CHOICE in who your friends are. Sometimes you have a crossover from both sides. I have a cousin that I call a friend before I call him family. I do this because I am not close with all of my family, but am close to all of my friends. In social interactions, calling someone a friend is possibly the best compliment you can give them.
The problem most of us have is that as we get older, we let our friendships drift. Many people in their late twenties and early thirties are concentrated so much on their job and starting their own family that they allow their relationships with friends to grow apart. My friends and I always got together every Christmas for about ten years straight, but as we grew older, moved further and further from home, and started getting married and having children, our annual get-together got harder and harder, until we basically abandoned the idea entirely. It still seems sad to me that we could not take one evening out of a 365 day year to all see one another again, but this is a decision, whether consciously or unconsciously, that each person made.
Philosophers and scientists agree that strong social relationships are a KEY to happiness. Researchers have found that people are happier when they are with other people than when they are alone and the “boost” is the same for introverts and extroverts. They also are finding that happy people are more pleasant, helpful, and sociable. So being around people makes us feel happier, and when we are happier we are more fun to be around, creating an “upward spiral” of happiness. Other studies have shown that people who are socially active are nearly twice as likely to be happy as those who are not. And if all that isn’t good enough for you, a ten-year Australian study showed that people with a larger circle of friends and those who had constant contact with friends were 22 percent more likely to live longer. So, if you are really averse to the dieting and exercise portions of this book, at least go make some friends. It’s healthy

Sources:
PBS.org
Happiness, by Ed Diener and Robert Biswas-Diener
Happiness Is Contagious
Positivity, by Barbara L. Fredrickson, Ph. D.
The How of Happiness, by Sonja Lyubormirsky