I believe this is a solved problem and you were closest with the analog system. I'll outline my system so people might find it:

You'll need:

- A physical diary to track your appointments

- A 'working' box to hold index cards of whichever size you prefer (I use 3x5 Exacompta cards)

- 43 tabbed index card dividers + some more if you want tabs for GTD-style 'contexts'

- A pouch for carrying index cards on your person (I have a Lochby Pocket Journal which holds plenty of cards)

- A box to act as an 'inbox' for you to dump cards into before processing them

Where you went wrong is keeping a list on a single card. The only solution is 'One Item, One Card'.

The Set Up:

- Take 31 tabbed dividers and write the numbers 1-31 on them. These will represent a day of the month.

- Put these in your Working Box

- Take 12 more tabbed dividers, write JAN-DEC on them. These will represent a month of the year.

- Put these in your Working Box /behind/ the daily tabs

- If you are using tabs to track 'NEXT ACTIONS' with contexts like GTD, write the name of the contexts on a set of tabbed dividers

- Put these in your Working Box /in front/ of the /daily/ tabs - as in, they come first in the box

Daily Routine:

- In the morning, sit down at your desk

- Check your Diary for any appointments you have that day

- Check your inbox for new cards and put them on your desk

- In your Working Box, pull out the cards that are behind today's day tab and move the tab to the next month. For example, today is the 28th of January, so I pull out the cards behind the 28 tab, put them on my desk, and then move the 28 tab back to February (which is already full of the 1-27 tabs from previous days)

- Sort through today's cards - I do this in 4 or 5 piles:

  1) Things I'm going to do now before I go to work

  2) Things I'm going to do today, but not right now - these go in my Pocket Journal so that I can refer to them through the day (things like "Call this person over my lunch break")

  3) Things I'm going to today, but when I get back home from work - these go right in the front of my Working Box, before all of the tabs. I also organise these into an order in which I am going to tackle them

  4) Things I'm going to move to another day, which I then move to another day tab

  5) (optional) things I am not going to do, but don't want to throw away. I put these into storage in a 'Someday' box which I look at once a week

- Go off to work with the cards you sorted into the (2) pile, and plenty of blanks to write down anything that comes to mind that you might want to do - make sure that you put one thing on one card, so that they can be sorted into the box easily

- Come home, dump all of the cards in your Pocket Journal into your inbox, and sort them out there and then or leave them for the next morning's routine

As jobs get done I either throw away the card if it was a one-off job, or move it to another day if it is a recurring thing. For example, I have a card that reminds me to clean my phone which I do, and then put back in the box in 2 days time.

Why This Works:

I've been using a system like this for about two and a half years. Before this I used Org Mode and spent a lot of time tweaking agenda views and tagging systems etc. Index cards work better for me for the following reasons:

- The system works offline

- It requires no technology, so I can have a productive day without touching a computer or phone, which is good for my mental health

- I work a job where I cannot always pull out a phone to take notes

- The act of writing things down helps me to remember that I need to do them, and stops me writing down frivolous things (think about how many people have a TODO app full of odd little jobs they'll never do which got there because there's no friction to adding things to their lists)

- Because I have a good habit of ...