Siri can add things to your Reminders app, so you can forget about them. I use it for grocery store things– when I think of something I need, I ask Siri to add it to my Groceries list, like this:
(If the list doesn’t exist, Siri will offer to create it.)
Using this technique, your Groceries list will grow item by item over a number of days, and when you go to the store you will have the whole list right there with you.