Let's say someone goes diving into shallow water without checking first and gets paralyzed, they're disabled despite it being their own fault.
Or someone chooses to chop off a hand, they're disabled despite it being their own choice.
Or someone is morbidly obese and unable to function as well mobility-wise or otherwise as others - well, even if the disability is in whole or in part based on personal choices, that doesn't mean the person isn't disabled.
It might be that for reasons of principle you want to treat disability caused or contributed to by personal choices differently - if someone does extreme sports, or motorcycles without a helmet, or uses drugs, or eats a lot, and suffers impairment of functions, then screw them (I'm not so unsympathetic). But if the question is just disabled or not, I don't see what the degree of self-contribution has to do with it.