The Divine Grace can completely change fate. And aspiration for the Divine, if it is sincere and persistent, not for this or that or any other purpose but the Divine, brings into action the workings of the Divine Grace. Even if the aspiration is not strong enough, then Faith and sincere Surrender are enough to cure an illness.
This does not mean that it will necessarily cure at once and as a magic. There are many complex, entangled knots in nature that need to be addressed. Certain illnesses have deep biological roots and are supported by some movements of our nature. Hence, they may take time. Others are simpler and relatively easier. But in principle, there is nothing that cannot be eventually cured by the Grace.
Affectionately,
Alok Da
