If you're talking about euthanasia, I have to say, I completely agree with it. I'd prefer to let someone end his life rather that see him suffer. And of course, if there's no cure, he'd be bound to die some day or the other, living with the pain before that. No incurable disease keeps the pain away. But I do believe if there's a cure, I surely wouldn't let the person to end his life.
Also, if it's just pure suicide, I'd consider it to be murder. Though some may say everybody is in control of his life, it just isn't right.