People often ask why it's me and not my older sister, Amy (who also has cf), who requires the lung transplant. Logically, it feels like the older person should require a transplant first. Unfortunately, cf doesn't behave logically and there is no way of knowing why I am the one who requires a lung transplant first.
Well, that's not true, the reason I need the lung transplant is because her lung function is significantly better than mine and she would not be eligible for one. But as to why my lungs crapped out before hers, who knows! Cf presents differently in everyone so although we have the same genetic mutation, there may be a variable that makes me more susceptible to infection.
Or maybe it's not genetics at all, maybe I was exposed to more viruses over my life or maybe I didn't exercise as much or maybe she didn't skip her aerosol mask that one time, or maybe...or maybe... the reasons could be endless. I've given up wondering 'what if' or 'what could I have done differently.'
The thing with cf is that there is such a slow decline in the lungs that it is hard to pinpoint overall health to a specific infection or behavior (unless you smoke or refuse treatment or something obvious).
So basically, I have no answer for you. I realize that isn't very satisfying but such is life.