My Father in Law is still on chemo- he's been on it for three years. Apparently the fuzziness is just a side effect- sometimes it goes away, sometimes not. It depends on the chemo.
What you're doing right now- puzzles, brain games, that sort of thing, is an excellent way to help the anti-fuzziness. Keep in mind it might take a while, even a really long while to fully go away or be under control.
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Sage knows our mythic history, King Arthur's and Sir Caradoc's
She answers hard acrostics, has a pretty taste for paradox
She quotes in elegiacs all the crimes of Heliogabalus
In conics she can floor peculiarities parabolous
-C'hi