If it's any consolation to you, I am also in my 30's (33), and live a healthy, active lifestyle - run a lot, lift a couple time a week, commute everywhere on my bike, I love half-marathons.
So to suddenly be stricken with this disorder is a real bitch. I spent a week in a hospital just the week before last, wondering why they were keeping me hostage! I felt fine!
Now I am on Prednisone, it's working out OK so far, and am back to running trails and riding my bike and I even went backcountry skiing last week. What I have learned is that I am more prone to hypochondria when I stay at home, than I am when I am out being active.
So don't let this get you down - just accept you have it, accept that it sucks, but think about the good this can bring to your life: appreciating it more for one, and staying healthy.
My first run after the hospital was pathetic! That was on Monday. I was huffing and puffing and my legs were weak. All week I continued to ride my bike and today I ran again alas still a little slower than before the hospital, but a million times stronger than just Monday.
So my advice is to just get out there, stay active, and bounce back.
It's nice to run into another person with ITP who is an active adult male in his 30's, it seems this really hits women more than men.
Keep it up!