As a child, I was rather sickly. I had things which raised eyebrows at my pediatrician's office, like mumps and scarlet fever. My acne in high school was so severe that I ended with with tetracycline as a maintenance drug.
A year of tetracycline was the turning point of my health. In the intervening 24 years, I have had no lingering sickness, and indeed nothing which has required treatment other than accidental trauma.
Step 3: learn respect for the physical gifts you've received.