You laugh, but I once advised a friend to write (most of) her passwords down on a slip of paper and carry it in her wallet
I once had to change my password every week for a project. I wrote it down.
My father writes his pincodes down as part of a phonenumber. e.g. have it as "John Doe 1-212-555-1234" where John Doe is a real sounding name and the phonenumber looks real. The last 4 are the pincode. (Could be any of them in any order. Also will depend on the country. e.g. the real pincode here could be 3215)
He has done that for number codes since at least 60 years.
He uses some sort of Monoalphabetic encryption which uses only one word and is even simpler as VigenÃre cipher as he can do it without any paper. And no, it is not Caesar cipher or anything like it. It is based on one word. Not sure what it is. He explained it to me when I was a kid and I forgot most of it.
This all from a time where he used (and still uses) paper agenda's and no access to anything electronic.
I personaly have 5 passwords. Work, Bank, Personal machines, Unsafe Internet, Safe Internet. The issue is that I often need can't remember my login as often you can not select your own login.
At one company I had 17 different logins with variations of my name, company or combination because the systems were handled by different companies. (Also had 3 digipasses.)
One had such a 'secure' system that we had the process (including the 3 differnt logins and passwords that were send to us each month) printed out and hanging next to the dedicated PC for all to see.
Yes, they were stupid enough not to give individual logins and/or digipasses, but insisten on a group password.