If a person wants to die, who are we to stop him? Although, of course, the person's disorder needs to be studied effectively. We can't just kill a person the moment they want to die. Many people have very wild mood swings so wanting to die one moment is countered by wanting to live at another.
I agree people deserve to choose whether they live or die but its difficult to determine whether the person 10 minutes or a week from that moment will feel the same. At the SAME time, who are we to assume that a week from then the person will want to live. If we always make that assumption a year, a decade, later.....then you are also doing one of the worst forms of torture imaginable.
Therefore, each case will have to be analyzed individually.