For the last 10 years I have been saying this should be legal. As long as you are determined to be of sound mind and not influenced by anyone, then let them make the decision. You will have many arguments against it (religion, could be cured unexpectedly) but it’s the patient’s decision.
The only argument would be if doctors and nurses should assist. This is a huge argument against state sponsored executions. Maybe a device that can safely and painlessly assist the patient could be a resolution.