I do not agree that suicide is never the answer. Consider the fuss about assisted suicide at the moment. However it ought not be both the last and first course of action considered. Many have lived through a black period to be grateful for later experiences. Assistance to change life, and ones attitude towards it, should always be available from society; without judgement.
No it is not a selfish act of self indulgence. It is more of a selfish act to insist those who feel they can no longer bear living should be forced to do so for your own personal beliefs. Sure it is hard on family & friends, but they should not expect a family member or friend to continue in torment just for their sake. Love, and the desire for what is best for others, works in both directions.
Whether someone somewhere appears to be worse off that you, is not an issue. Should one be happy because someone somewhere is having to cope with greater hardship ? It is a nonsense comparison. Using that logic only one person in existence is "allowed" to feel despair at any one time.
The experience of life is not a black or white issue. It's value to an individual is measured by them in terms of perceived quality, not simply length.