Why is it selfish ? Is it not also selfish that you want them to stay in the tortured state that they may be just so you don't have to deal with them being gone? Would you rather they live a life of pain just to satisfy you?
It's sad for everyone left, but maybe no one was there to help that person descend further and further into pain until they couldn't deal with it any more? Would you want them to live like that?
Religious people (or those with a belief in some form of god) tend to call it selfish, but if there is no proof of a god what compunction is there to follow the "holy" books?
Sorry for the little rant there, I just get annoyed with people blaming the person who has died. They did it for a reason (whatever that may be) out of their own free will.
NB. I am neither for or against suicide, and I sympathise with those who have lost others to suicide. And sorry for thread-jacking, please return to the topic of knives.