Comments of chapter undefined of Darth Vader in Marvel

in the Star Wars comics he explained that Darth Vader refused to heal himself, or to have more advanced armor. It was then that Palpatine himself offered to have him build more powerful armor. but he refused in order to atone for the mistakes he made, and to never forget his loss of Padmé. he uses the pain his armor gives him to strengthen himself through self-hatred and anger to become stronger.