Pastor Rick Warren of Saddleback Church says it is not easy maintaining friendships, because people have to be purposeful and intentional about keeping their circle of friends.

"The starting point of building great friendships is investing your time and energy. Deep friendships are not accidental. They are not instant. And they are not cheap," he writes on his website. "Deep friendships are...a choice."

The key to establishing friendships is to start getting interested in other people's lives. In fact, Warren says in doing so, people will "make more friends in the next two months than you would in two years of trying to get other people interested in you."

Even Philippians 2:4 says so: "Do not be interested only in your own life, but be interested in the lives of others."

After the friendship has been established, Warren says the only way for it to grow is for people to be physically present in their friends' lives. If people don't "show up" for their friends, Warren says they'll revert to being mere acquaintances.

"Just show up. Physical presence is essential to having a long-term, deep friendship instead of an acquaintance," he explains. "When somebody says to you, 'You know that small group this week? I'll be with you in spirit,' you know what that means? Nothing! It's a bunch of bologna. You can't be in spirit anywhere. If you're not there in body, you [aren't] there. Friends show up. They're present."

Meanwhile, Warren also has some advice on how people should build their family legacies. The "Purpose Driven Life" author believes that "awesome families" dedicate their time in showing love to their neighbours and doing charitable acts.

"Awesome families teach their kids that they're not the center of the universe. They teach their kids that God made them and shaped them for a mission. They model dedication, service, generosity, and prayer. Average families don't do those things. Awesome families do," he says.