Disease = un-health - a state of being unhealthy. It does not mean a state of dying. To say life is a "terminal condition," or a state of dying, is akin to saying life is a part of death, or, life is death. To say life is death, is an oxymoron. There is life, and there is death. Never the 'twain shall meet.

While alive, one should be (ideally), living in a state of health. Saying all diseases are healable is simply saying that living in a state of un-health is a temporary condition that can be cured. God's will is for all to live, and while living, to be healthy.

There are times we are sick, and consequently, this suffering is allowed for a purpose greater than our understanding. However to end our suffering via our own hands, because we feel suffering is worthless or too great a cross to bear, is a sin. It's a sin because we are trying to be like God, and destroy life. We don't have that right - only God the creator, can decide who shall live or who shall die.

God always asks us to choose life. Life is hope. To choose death, is to choose evil. It is a sin in its most severe form.