Most important thing in life is to realize what "I" means.
Is "I" this present body or is it the soul.
The goal of all religions is to realize that "I" is for the indestructible soul and not for transient body.
All the suffering is for perishable body(including mind) and not for the cosmic soul.
For a common person, It's not easy to differentiate between one's physical body and one's spiritual soul, only few divine meditators can achieve that.
But everyone has the ability to start thinking in this direction.
So it's a powerful feeling when facing a disease like Cancer that someone can say:
I don't have cancer, never had, never will be, with the divine realization that soul is just pure energy and is part of Universal God Consiousness.
Yes, my present human body has cancer which I will fight till end to save as it has been a good vehicle for me.
In case I am not able to save my body, I will still survive, disease free and join the Universal Cosmic Consiousness and look for another vehicle suitable to my energy/frequency/vibrations profile.
Souls change diseased human bodies as Human bodies change worn out clothes.
I will never die, though my present human form will evolve into another form. This thought can have a powerful soothing effect on all minds.
Some say Soul weighs 21 grams: (though I am not entirely convinced)
http://en.wikipedia.org/wiki/Duncan_MacDougall_(doctor)