I carry 3x5 index cards and a pen with me everywhere I go. When I think of things I need to do, should do, or could do, I write them down. When I get home I see which ones are worth keeping. I put them in a box which has dividers for contexts, like GTD, and a 43 Folders system so that I can schedule stuff for future-me.

That is what you need to get things done every day in a reliable way. Everything else is bs. You don't need it.