Keep getting sick/hurt; how do I keep motivated?

I started training for triathlons in February, when I bought my first bike.  I also purchased my first pair of minimalist running shoes, which after my first two runs, hurt my foot, and I had to take 2 months off running.  During this time, I focused on biking and swimming, and went back to my Brooks Adrenaline's.  In May, when I started running again, I got the flu for a week, and soon after competed in my first Sprint triathlon.  Soon after, I got better, and continued my full training for a couple weeks before I got an eye infection which lasted two weeks, and had to take a break in my training.  Well I get better, train again for a full week, and get what I could only imagine was slight valley fever (I say imagine because I had absolutely no time to go to the doctor, but my roommate, a nurse, was pretty sure).  A week after this happened, I went home to Chicago and did the Lake Zurich Olympic Triathlon.  Rested a week, and then ran 3 miles, and now my freaking knee is tight and swollen, 1 1/2 weeks before my first 1/2 marathon in San Francisco!  It just seems no matter how much rest I get, something new comes along and makes me stop. 

I guess my question is how am I supposed to keep motivated when I keep having these things stop my progress?  I love reading triathlon/S/B/R books for motivation, but at this point I don't even want to read them because I feel like I can't put any of what I read into practice because when I get better I feel like something else will come along.  So how do you guys keep motivated and focused when you get hurt or sick?