Assuming we are only speaking of physical ailments here, I'd banish my lifelong problem with overeating. I would LOVE to just think of and react to food like a "normal" person, for once ... eat only when I'm hungry, only enough to make me not hungry, and decently healthy choices. I would LOVE to be rid of the addiction to carbs, sugars and fats that has consumed my life since I was old enough to feed myself.