My first spat with cancer was enough to require chemo and, I swear, I lost IQ points after the second dosage. I went from knowing all sorts of shit to not knowing how to play songs I wrote, recorded and played hundreds of times. I went from having a sanitized, orderly home to having piles of clothes and tools. I'd search hours for things only to be told I hadn't had it for years.
I also lost my patience for stupid people. All of it.