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Honestly 2 days is entirely understandable to forget.

When I change such an important password (which is very, very rarely), I keep a hidden hard copy for a short while, until I'm confident I have it memorized (usually a couple of weeks). While this has some risks, obviously so does losing access to your data. It depends on your living situation and threat model.

I'd say that falls into the "reasonable to forget" category, considering you still remember most of it, only typed it twice two days ago and aren't sleeping well (etc.)

What might help jog your memory is 'reliving' the moment you reset it, e.g. re-reading or watching what you were doing before, whatever you were thinking about, listening to or doing at the time and right before it. It might help you to reconstruct the train of thought that led you to choosing said passphrase.

I don't rely on myself remembering anything before repeating it like 100 times, over a month or so. 2 times, then 0 for 2 days, is almost guaranteed "puff" and it's gone.

Think of memory like this: how many times back, do you remember taking a piss? The last one? the one before that? what about 10 times ago?... but I bet you know by heart which side of the toilet you keep the toilet paper, don't you?

We are primed to forget "irrelevant" things, and keep only what matters. Something you only did 2 times 2 days ago, tends to fall into the "irrelevant" pile. Repeat it 3 times a day for 30 days, and it will stay in the "relevant" side. Keep repeating it for a year, and it will end up in your involuntary muscle memory.

For important password changes, either write it down at the beginning, or practice remembering the new password a few times every day, for a week or two before actually changing it.