((Prussia takes pain for others. There are a number of times where he’s taken pain in order to protect his brother, that goes without saying. When he goes to visit Austria and gets hit by Hungary and everything, he’s taking pain that they feel into himself. He doesn’t have to keep going back. He knows it doesn’t usually end well for him. He does go back though. He increases his own pain to lessen that of others.
Being in such pain doesn’t mean much to Prussia anymore. He doesn’t feel much purpose to himself, and there is an obvious void, so he fills that void with pain. Feeling pain is a reminder that he can feel anything at all.))