I cannot imagine life without friends. They are a "safety net" that holds us up during each stage of our lives. Some friendships die naturally, but there are also those that last a lifetime. There are old friends and there are new friends. I don't make a habit of closing myself within one circle of friends, but that does not mean that I would leave my old friends for new ones.
In my opinion, it is very important to make friends in circles different to our own: other countries, customs, religions, and even ages. These types of acquaintances and - hopefully frequently - true friendships, enrich us, broaden our horizons and help our self-development.
Friendship is like a two-way street - I count on my friends, but they can always count on me too because, as the saying goes: "True friends are those, who are there when you need them"!