Is it too late?

[Siren]

I'm wondering, is it too late at this point to alter my polarity?

No. Do not concern yourself about temporal matters. Live in the now. Polarity can be "reversed" in an instant, if such were the case.

My other question is, when the Ascension comes, and when the majority don't actually ascend, will they remember that an ascension happened and they missed out?

It is my understanding that, no, they wont remember (because they didn't ascend/graduate; they can't remember something that didn't happen).

I also read that when Ascension comes, the people who don't ascend will for a moment feel "at one" with the Infinite Creator, in zero-point time, and will get a reminder of who they really are, and then a "veil of forgetfulness" will descend upon them.

I imagine something like that could occur, but I'm not particularly concerned about it. I suppose that as a planetary sphere spirals into a new vibratory spectrum (4D in this case), some sort of side-effect would be experienced even by those entities that are to repeat a 3D cycle (elsewhere) whilst the others graduate into 4D. I believe some sort of "blast" in consciousness would be experienced even by the "blindest" of entities. But I also imagine many of these entities wont have any idea of what (or why) they are going through.

Does this include forgetting about missing out on the Ascension after December 21st?

No fixed date. Ascension/harvest/graduation is NOW (and has been NOW for the past couple decades and years to come).