Grief for someone who has not gone

The inevitable mourning that occurs when a loved one suffers from mental illness has been striking me recently.
Theoretically, I know that, from a medical point of view, that mental illness is not different in type than physical illness. I know, as a physician, that mental illness should not be a stigmatizing status, and that its sufferers should be seen and treated with the same amount of respect and care that we would for someone with, say, an amputated leg.
The practical reality is, however, quite different. I have been mourning quite deeply for a loved one that I am not entirely sure will entirely come back to reality (see, I'm crying right now thinking about it). I am not sure if it is because that the value that is placed on being of 'sound mind' is incredibly heavy. I am not sure if it is still the huge stigma that is still associated with mental illness. I am not sure if, in my culture and in my social group, that having a quick-thinking, 'normal' brain is expected. I am not sure if we, as a society, truly believe that people with mental illness really are the 'same' as the 'rest of us', and that we actually believe that they suddenly become 'apart', that they are no longer allowed within the realm of 'normality', that we mourn their exile into the abyss of disreality.
The disconnect between what I know as a physician, and how I experience it, as a friend, has been repeatedly slapping me in the face. My friend is still the same dear friend that they were last week, last month, last year. This, just as if they had had a heart attack, been diagnosed with cancer, or lost an eye. However, I fear for their future: for their family, their work, relationships they may have, and how God will deal with all of this.
Now, I know this fear is irrational: God is firmly in control, and He is always good. I trust that He will watch over them, and His ways are things that I cannot understand. Which is why I will not mourn in front of my friend: I may fear and worry, but it is not for my friend to bear my burdens on top of their own. The load that they are now called to bear requires me to help carry it, not to add my own fears and sadness onto it. I am already worried about them in how I have seen family members and friends heaping their own anxieties onto their frail shoulders. It grieves me as to how this will affect their healing, and the role that they may be assigned by the fears that have already been projected upon them, even this early in the proceedings...