I’m very sorry to learn of your illness. I was asked much the same question you pose a few months ago by another correspondent, who had been told he was suffering from a terminal disease and was writing to request my advice about “spiritual” books. Here, if you’re interested, is what I told this person: Mental Health and the Classics.
But yours seems a very different case: for one thing your sickness isn’t immediately life-threatening, at least as far as you know, and for another you’ve already read Plato—perhaps even more times than have I!—as well as Dionysius and Boethius. And though Ramana Maharshi is new to you (or so I gathered from your message), you’re nonetheless familiar from your studies of Madhyamaka Buddhist philosophy with much the same intellective strategy, which consists in pulling back from the demands of the seeming self by objectifying it and subjecting it to a dispassionate analysis. A reading list along these lines would seem quite beside the point.
It is perhaps worth noting, however, that one of the authors in this list, namely Boethius, was only three years older than you when he died. Did you realize that? I suppose the kshatriya in you may say that bearing a martyr’s death would be much easier, because more glorious, than dealing with your own present sufferings, trivial though they may appear by comparison. Perhaps, but the Consolation nonetheless suggests that its author felt his fair share of “trivial anxieties” as well! Maybe rereading his book—surely one of the very greatest of all the “great books”—in this light could be a useful meditation for you.
There’s no guarantee, of course, that this will free you from anxiety about death. Nor, I hasten to add, is freedom from anxiety necessarily the unmitigated good you (not unnaturally) imagine. It may well be that your feeling of dread is precisely the God-given means you require to provoke a keener interest in disciplined spiritual practice, the interest you have so often confessed you don’t have. Could it not be that these present sufferings are but a wake-up call to your soul, a true memento mori? Not even the quintessential orison of the Heart can, or should, “cure your anxiety”, and it would be the height of foolishness for me to promise such a cure, or for you to expect it. On the other hand, what I can promise is that faithful perseverance in this mode of prayer will give you the distance you need to observe your anxiety with an increasing dispassion.
This “distance” may at first persist only a heartbeat or two. Eventually, though, the practice will lead to a point where the anxiety is no longer needed and dies away of its own accord. I have no way of knowing when you will reach this stage. But whether it’s on this side of your death, in the midst of your dying, or after your death makes no operative difference. The point is simply that a continual, attentive return to the Name is an excellent way to prepare for that death—as do all those who (like Plato) “pursue philosophy aright”—whether it comes (as you have worried) very soon or only many years hence.