My experience was that I was pretty mild for a long time, and then last year totally knocked me for a loop! I was in and out of the hospital more than 6 times, and ended up needing to take a year off work and be on disability. Needless to say I was very worried that this was setting a precedent and that I should be more than a little concerned about what sort of future I would have.
My doctor allayed my fears and said that with CF, sometimes you just have a bad year. My "bad year" was truly awful, and in Dec. of '06 I very nearly died one night in the hospital. Since then I've rallied like you wouldn't believe, and have, with the exception of the last 2 weeks, had a wonderful improvement in my status. I've gained weight, improved my stamina, and regained some lung function.
This may just be your "bad year" or "bad season." Don't let it discourage you. Instead, let it motivate you to do what you can to make any necessary lifestyle changes (for me, I needed to rest more and take a lighter load at work).
All the best,