Without going into details (and making clear that it was in-no-way life-threatening); my recent illness was an existential challenge, and unique in my life so far.
This was because it combined the most extreme malaise I have experienced (exhaustion, demotivation, anhedonia, anorexia); with at least two simultaneous unremitting and severe forms of pain/ dysphoria (of several types, throughout).
(Note - I use dysphoria to mean the opposite of euphoria - as a generic term that includes all types of pain, but also all other acutely-unpleasant pain-like symptoms such as nausea, heaviness, and that drained and 'washed-out' sensation characteristic of 'flu').
Consequently, for a week, I was always in an acutely miserable state; plus I always lacked energy, concentration and drive.
The horrible result was that for that week I was horribly selfish and self-centred; and insofar as the wider world impinged on me, my attitudes to everything were wholly negative and pessimistic. I was disgusted at myself for this; but such disgust merely added to the negative-mix - it did nothing to combat the fact.
The fact that I understood, theoretically, just why this should be: why (in a pathological sense) it was happening; this was of surprisingly little or no help - certainly it did not make me feel significantly better. Thus I could only escape the horribleness of the closed-world of selfish-self-centredness for a few moments - after which the default state inexorably re-imposed itself.
Furthermore, I was reduced to an almost-wholly non-spiritual level of functioning. Meditation and (meaningful) prayer were eliminated; all the perspectives of a joyous and hopeful nature were experienced as mere forms-of-words or futile actions - and anyway lasted only for very short periods before the mind would return to its miserable brooding.
Some of the lessons I took from this included that there are situations when circumstances are stronger than resolutions and convictions; and where positive efforts are so feeble and short-lived as to be swamped.
I see how some kind of illness, sufficiently sustained, could easily overwhelm whatever defences were in place; and could poison even long-term and deep patterns of good attitudes and behaviours.
I hope that in future this makes me more empathic towards those who have become narrowed and petty as a result of sickness or circumstances, too strong and lasting for their resources to resist.
In retrospect; the experience has confirmed my understanding of this mortal life as a time for spiritual learning - and not (or only very seldom) a phase of solid, incremental, spiritual progression.
In other words: theosis is properly understood in terms of what we have learned spiritually during mortal life on earth, being recognized of value to our immortal resurrected life in Heaven. Theosis is not, therefore, about making ourselves better Christians throughout mortal life - such spiritual improvement being detectable and evident during mortal life.
If I had previously supposed that I had made significant spiritual progress as a Romantic Christian - then it would have been devastating to see it all swept-aside so 'swiftly and effortlessly' by a combination of physical symptoms.
Instead (now that I have emerged from it) I can see that this state of malaise-dysphoria (during which I could find no positives and was crushed by negatives) functioned as an experience that was intended to be learned-from - but learned not while-it-was-actually-happening; instead, learned in retrospect.
My main conclusion is that life can get the better of us!
We can find ourselves in situations where no amount of positive thinking and spiritual hope (nor of medical intervention) can alleviate the situation.
Unavoidable suffering just-is part of life, part of the divine plan for each of us (and for some more than others).
We will sometimes find ourselves 'inside' an inescapable adverse situation - and while that situation continues we can do nothing more than cope as best we may.
The challenge comes afterwards - looking-back; when we are called-upon to make sense of it.
That is when our Christian faith should come into its own.
Note: I am here trying to draw general conclusions from a personal experience - I am not soliciting advice or sympathy. Also I will not publish any comments that aim to be reassuring or consoling: that is not the point of this post. Nor am I looking to compare notes with others having had what seem like similar experiences, except insofar as they contribute to this overall aim.