In my case wanting to die isn't an "illness", it's a rational response to existing here in this harmful and dreadful world where we are destined to suffer more and more as time goes on. Existing just doesn't appeal to me anyway, it's a futile burden and a chore, I think it's always preferable to cease existing no matter what as nobody can be harmed by not existing, to die solves what the true problem which is existence in itself, existence could never be a desirable state, the existence of life is a cruel, tragic mistake and there's no value to slowly deteriorating from old age which is all that existing leads to.
And to me the absence of everything is true peace, existence is just an unnecessary disturbance in what would otherwise be the perfect state of non-existence, there is no peace to be found in this hellish world, it only exists in nothingness.