For me, with a tracheotomy tube and a windpipe with scar tissue that doesn't seem to want to properly heal, a suppressed immune system, and the extra baggage that comes with CF post-transplant, I know there are limitations to what I can do. The adage You can be whatever you want died long ago. But I must pursue what I can within reason; follow my dreams as far as my health will allow; compromise where I need to; redirect. What makes such a demand so difficult is that there are times when I am so healthy and full of energy that I can do the work of two people. During those times, I take on as much as I can so I can make it worth it. I seamlessly juggle full time work, marriage, family, volunteering, mortgage, book promotion, and grad school on the side. And then I slip and everything scatters. I find I am great at commitments until I can't be.
My advice to you, fellow transplant recipients, fellow CF patients, fellow survivors of chronic illness, is that no matter how much you take on when you are well, be sure that each entity will accommodate your circumstances. First and foremost, find a career that will be flexible when you need it to be. That does not mean you can't handle a demanding job, because many of us can; it just means you need that demanding job to accommodate your health, not the other way around. Some people might not feel comfortable disclosing their chronic illness with their employer, but I say the people you make long-term commitments to should know and accept that sometimes your situation switches with the wind - you catch a cold that turns to pneumonia in a few days, your body does something wacky, new medical demands fly out of nowhere. That takes a lot of stress off you worrying who you might disappoint. It can also make it easier to plan ahead.
Most importantly, you need to accept the fact that life can change more quickly than you want it to. If you resist, such change will be more painful than it already is. One month I was a new college graduate, on my way to Lake Placid with my family and knee-deep in freelance writing projects I had committed to; the next month, I was on an operating table, the doctors scrambling to get a pulse.
You know that your illness won't allow you to ignore it, so don't plan as if you can. Instead, plan with a degree of openness: with your spouse, your family, your employer, your teachers, and so on. Let them in, even just a little, so they can see that there may be times that you need to reroute before your illness takes the steering wheel. Lastly, remember that you always need room for enjoying life. Just because you need flexibility to handle your medical demands does not mean you shouldn't also expect room for happiness.