With this curse, your sense of pain is completely warped, causing your body to find it unnaturally soothing and enjoyable - and at more extreme levels, borderline pleasurable. This also overrides any Perks, powers or other abilities (such as alien/eldritch physiology) that would normally negate or help you deal with pain, reducing their effectiveness to a quarter at most and capping the pain reduction at 50%.
Curse of Sadomasochism
Not even the self-inflicted torment of the Curse of Pain is immune to the Curse of Masochism, and in fact the two Curses even synergize with each other: Not only does the former make it easy to get addicted to the latter’s warped sense of pain, it also makes it similarly easy to get addicted to inflicting it on others as a direct consequence. Try not to go overboard.