One habit I've had for a long while is I like to dictate to myself. I'll record voice memos into my phone, often as I drive by myself. I use them to jot down ideas about fiction I'm working on, or story ideas when they come to me.
I often forget that I do this, too. Then when I go to record something, will stumble upon old recordings I've made, and listen to them. Sometimes when I do, I'm shocked, amused, or thrilled by these forgotten gems, that connect me to ideas long forgotten, or some way I was feeling that I no longer do.
Just today, I was taking notes for my next novel (working title, A Little Patch of Sunshine), and after I finished, I stumbled across this idea for a horror novel.
I completely forgot about it - and when I listened to it, was actually terrified by it, and its conclusion.
I have a long list of writing projects ahead of me, so I don't know when, if ever, I'll get to this one. But I'm glad I recorded the idea - because it's a thumping good one.