Everyone has a personal idea of friendship and so there isn't the same answer for this question but I think that a good friend should be a person who accepts you, with your strengths and weaknesses, who has got that character and that personality that combines perfectly with your own.
It isn't easy to find a good friend but I think that everyone will find him/her sooner or later because he/she is fundamental to our life. He/She always listens to you when you have a problem and he/she will always try to tell you adevices to help you, he/she understands what you think and he/she will never judge you, a good friend will always tell you the truth, th at which makes you feel better and also that which hurt you but he/she wiil do it only for your own good. You can talk and discuss about everything, you can share your interests, you go out with him/her and you have a lot of fun.
But you can also get angry or argue with him/her knowing that it will not last more than a day because you are fond of him/her too much. This is a good friend for me and I'm lucky because I've already found a good friend like this.

WHAT MAKE ME SUFFER

I think the words can hurt more than a slup, something may hurt me if it is about arguments painful by themselves, which I'm trying to overcome, I may also suffer if I find an important person for me not to be like we imagined and we realized he/she lied for a long time. I may suffer for others when we see someone have a problem but we know we can do nothing for him and anyway we don't manage in accepting it.I may also suffer for reasons which don't depend on others,for example if we are not like we would want to be, if we don't feel well with people and we fell lonely,if we don't know what we would want or we would want to become. I often manage to overcome them thanks advices of my friends. Infact I wanted to avoid them because I wanted to hide pain, but my friends told me that to eliminate a pain I must face the problem if not it may be come back and hurt again. There are a lot of things which can make me suffer but everything depends on the person and on the moment and the only way to overcome them is face the problem.