this is pretty much the same rift that divided the Anabaptists, i think. The Book suggests Blessed Assurance, yet ultimately only the "hope" of salvation, which is to say that it is likely completely improper to consider oneself "saved" right now, at least completely and at every moment, since this would depend upon whether you are manifesting Grace or not, and you may not be.
Salvation is reduced to an on/off switch that gets thrown after one ticks off enough boxes on their religious worksheet iow, and at a certain point one i guess gets enough "faith" that they just start claiming to know stuff, to know God, or to know what God thinks, or at the very least know what constitutes a "saved" person, at least enough to commend them to someone else as being "saved."
So imo what you have here is a logic trap that will engender pride if one seeks pride. At the least the effect of Tares should be considered here, which would have an affect on this "knowing," it seems to me. Know, but be willing to question your premises iow. Know, but see that you cannot know, looking through a mirror, darkly. Keep a sense of not knowing also, lest you begin insisting upon things that may have been true then, but are not true now.
Because it seems that as soon as you demand "knowing" something, you have to in a sense put flesh on it, embody it in a concrete meme, the Thing You Know, that is defined like this and like that, and that does not have one of those, etc; and then you maybe even write down what you know, that others should maybe take to be inviolable, this definition of something you all know together, now. That will not always be true.