First of all, I don't believe in destiny, but if it was something like that to happen, then I guess the paradox is not even a paradox, its simple. If you are destined not to heal, you will heal even if you don't go to a doctor.Miracles or exceptions or whatever happen. There are 2 people in the world who have been cured by AIDS.Nobody knows how,but they were diagnosed with AIDS and now they are cured.Cannot be explained,but it happened.
I will give you another example.
My mother told me from her doctor that he(the doctor) had a patient that has gone through a lot in his life.Hit by a car and survives.Then, he falls from a tree.He has 8 broken ribs, but survives.Then one day he is diagnosed with cancer.The doctor gives him 6 months. After 1 year, the doctor meets that person who seems to be as healthy as an ox.
Maybe there is something.Maybe not.But the paradox is not a paradox if one can accept that miracles happen.And there have been many miracles in the world.Known and unknown.I`m an atheist by the way, but such things happen.