My own idea, for what it is worth, is that all sadness which is not either arising from the repentance of a concrete sin and hastening towards concrete amendment or restitution, or else arising from pity and hastening to active assistance, is simply bad; and I think we all sin by needlessly disobeying the apostolic injunction to 'rejoice' as much as by anything else.Humility, after the first shock, is a cheerful virtue.
C.S. Lewis, The Problem of Pain
optimism