Meh, I don't know. It's nice to be able to have the occasional chocolate bar or milk shake and have the only consequence be salad for dinner for a night or two, not a session of either messing around with my insulin or saying to hell with it and begging for complications. I live by myself, I mow my own lawn, I go up and down stairs, even at my craziest; can't do that with no legs. I'm so nearsighted in one eye that I don't have any depth perception, so losing it wouldn't make much difference. I've watched a lot of people die from cancer, including my parents. I'd rather be bipolar - no matter how much pain I'm in, I can always get up and go to the bathroom, I can (although I might not) feed myself, and I can turn over in bed. You don't have those options in end-stage cancer.
And the thing is, is that bipolar disorder is treatable. Not easily, no 100% symptom free guaranteed, but enough so that one can get along. I'd rather have something like bipolar disorder than a personality disorder, which can't be medicated per se, but instead requires intensive therapy, which horrifies me more than a life on meds.
And to go completely Pollyanna on you:
Life is not a matter of holding good cards, but of playing a poor hand well. (Robert Louis Stevenson)