friendships

What constitutes a good friend? Can they make you feel bad sometimes? Are they allowed to? Are there rules to friendship? How does one know these rules?

If one breaks these rules, and makes another person unhappy and you are unhappy, does it mean that the friendship is no longer good and it would be better to be over, or do you TRY TRY TRY to make it better? How do you know what to do?

it is a dilemma. they don't teach you this at school.