So the other thing about using index cards is that it's incredibly flexible.

In my case: I'm a decent home cook, but I struggle with meal planning and groceries. So my solution here is to create tiny recipe cards I can assign to specific days, and as I assign them I can list what we need to buy from the store.

But this doesn't just work for meal planning, you can do the same for workouts, music practice, hobbies, and so on. Anything recurring you want to make time for!