There is a saying : "A friend in need is a friend indeed".
And I absolutely agree.
It means that if your true friend needs your assistance, he may rely on you.
To be a good friend means that you are ready to help your friend any time he asks. Even if you are busy you'll find time to help your friend.
A good friend is always easy and pleasant to be with. Even when you feel blue he'll cheer you up.
It's very good to have a true friend!