Euthanasia

The act or practice of killing or permitting the death of hopelessly sick or injured individuals (as persons or domestic animals) in a relatively painless way for reasons of mercy. That is the dictionary definition for euthanasia. It's common to hear about animals being put to sleep because they are old and suffering; it happens quite often. Should the same rules be applied for humans? I think that if a person has a terminal disease (such as cancer), then they should have the choice to just die now without suffering and living in pain, but only if they don't have any chance of surviving the illness. Suffering isn't fair, because some say that in an after life, we will go to a better place. I don't have complete faith in an after life, so in my view, life is all you have. I would not want to spend my precious years on earth in suffering. What is the point of living if you die in pain? If someone has a mental illness, then things are different. If the person is happy, then thats plenty of reason to let them live on. If they are enjoying life, even though they may not have a full understanding of it and of what is going on, they should be allowed to live if they are truely happy. Now, what if a person does not have a mental illness, but is completely unhappy and they think that their life sucks and will never get better. If the person is living in a depressed state for the rest of their life, should they have to live on? Or should they be allowed to die or be killed? I don't think that a life should be thrown away. If someone is curable, or has some hope, feeling, or love then they have plenty of reason to live on, but what if they are suffering inside? I guess each situation is different, but mercy killing sounds fair only if the person agrees to it, they are truely suffering, and would somehow die anyway. I think that the best way to deal with it is to choose the path that will make the person truely happy, whether that be death or not.