4 Types of Friends

I just finished a book called "When Men Think Private Thoughts", and it basically talked a lot about the various things men usually worry and think about. One interesting thought that the author (Gordon MacDonald) wrote about was about the four types of friends that men should have. He was inspired by these four types of friends when he went on a skiing trip in Colorado. Here are the four types:
"Ambassadors" - one who simply wants to enjoy the ride with you
"Lift Attendants" - one who wants to maximize your experience by helping and serving
"Ski Instructors" - one who's there to make sure you're growing and learning
"Ski Patrol Members" - one who holds you accountable to keep your commitments and your purposes but who's also there when you're helpless and broken

So, do you have all four types of friends in your life?