In keeping thoughts to yourself, there is a feeling of security in knowing that secrets are safe and nobody can judge. Of course, since nobody can know.
He knew this and practiced this. The feeling of security was well worth any downsides, as past follies clearly illustrated.
Small wonder then that when the chronic illness showed itself for what it was, he was in too much shock to understand. Denying, refusing and all those funny stages of non-acceptance were followed by a resignation to where he was. There was no way back, he realised. He would live now, without it.
Remembering unemotionally the days that had brought him to this, the childish pains and the immature temper followed by that petty age of revenge and sleep-depriving ego, he could see himself cutting off the connections.
Now he didn't know what he did. Or why he did it. Why did his friends all leave him? Why couldn't he explain his moods or his reprisals? Even to himself!
Slowly, with a blunt knife which sharpened with use, he had severed himself. And become the man who had cut his mind away from himself.