Perhaps you're right. If it's ruthlessness you seek then I think I can oblige.
That's partly true.
If the consideration of some truth caused oneself to suffer, yet we could act to change it (such as one's being diagnosed with some treatable disease), then the consideration of that truth would still be of value - as the necessary precondition for any possible solution. You can't schedule an appointment for your cure if you lack the balls to know about your disease in the first place.
If at any point there was nothing to be done about it (no solution and no reason to update either one's knowledge about or plans which incorporate it) then to cause oneself pointless suffering by dwelling on it would be immoral. Remember Rearden's response to the Equalization of Opportunity bill.
The purpose of knowledge is action.
However, ignoring an irrelevant issue is not the same as active evasion (provided one pays it due attention whenever it is relevant); that's one of the things that "thinking in essentials" demands. If I responded to the OP with some remark on how Trump should deal with North Korea, for you to ignore me would not be an evasion (and to give me a serious response would be fallacious).
Finally (although you must judge the relevance of this) I emphatically disagree with the equation of flourishing with "bliss". "Bliss" connotes a certain passivity (the thought that comes to mind is relaxing into a food coma after Thanksgiving dinner) which -while not necessarily a bad thing- is completely different from the emotional quality that drives a Roark or a Galt. The type of "happiness" distinctive to Egoism is fiercely active to the core (the very possibility of its experience requiring that we first push ourselves beyond our limits). It's neither compatible nor with a food-coma type of "bliss" nor with the cowardice it takes to evade a fact of reality. I don't believe it can be gotten that way.
You know that scene where he's standing over everyone else's bodies, pulling their plugs one-by-one? You do realize that he was signing himself up to live with exactly the same vulnerability, to strike him down (with neither warning nor any possibility of action) at any moment? Signing up for that is not a recipe for flourishing - nor is the mindset it'd take to want it, in the first place. 'True terror is being delivered to destruction blindfolded with one's hands tied behind one's back' (AS).
Cypher was the moron who thought he could be happy (whether in the Matrix or out) regardless of his physical survival. Honestly, the thing I find most amazing about that allegory is that the Wachowski brothers wrote it into their own damn movie and apparently have yet to think too deeply about its meaning.
I suggest you think twice.
I am sorry if my earlier post ("if you do it in the same manner you wrote the OP") seems to contradict this, but I didn't believe you could in fact do such a thing. Nobody can. I kept it to myself out of something like compassion (you sounded so depressed already and you're one of the only people I actually like to talk to) but if it's ruthlessness you seek...
Cognitively, in the long run you never could've kept your one evasion separate from the rest of your thoughts because all knowledge is interconnected - and if you choose not to consciously accept this then your subconscious would've done it for you.
If one science had contradicted your evasion then you would've started subconsciously looking for reasons to reject it; if another had supported it then you would've started looking for reasons to support it; to consciously suppress either (reminding yourself of your "one evasion" -like in the OP- and choosing not to let it proliferate) would constitute the kind of evasion which wouldn't permit you to forget its nature - and consequently wouldn't do jack shit for your emotional state (and consequently you wouldn't be able to do it for long).
-Mental Health versus Mysticism and Self-Sacrifice by Nathaniel Branden
Emotionally, the idea that your lifespan is infinite is not compatible with the constant, overarching sense of urgency in everything done by each of Rand's heroes (again, 'I only have, say, sixty more years to live'). You simply cannot budget the time that's yours to spend if you think it's infinite; you can take my word on that point because that's the single biggest thing I'm still struggling to "get" to this very day (specifically because I was raised with such a belief).
I don't know if it's because the Mysticism of your type of "deism" was so minimal or because of rationalization or what, but you seem to be having significant trouble with projecting the psychological state of a mystic. So let me indicate one possible example:
"If I had a voice I'd sing" - but I don't. If I had a mouth I'd scream.
Evasion is very bad for your psychology.