Modern living

With the addition of the 2 new email addresses required for graduate school, I now have a total of 9 (yes, NINE!) email addresses. Since I use fetcher and forwarding programs, I don’t have to check them all constantly (the programs redirect all of them to one email, so I only have to check that one), but I have to remember them all, and their requisite passwords.
I know that computers only have a specific amount of memory space. Do humans?
I know I have only a small (very small) space for remembering numbers. And my unwritten to do list never gets accomplished because I am always forgetting things. My unwritten grocery list meets the same fate. Am I exceeding my memory allotment in these instances?