In Remembrance of - That Thing I Forgot

Someone said that if something is important enough, you'll remember it. So don't bother to write it down.
I sort if agree.
See, the problem is, fine, if it's important I'll remember it, and if it's not I'll forget it. Fine and dandy.
But see, the problem is, sometimes I don't remember it, BUT I remember that I forgot something. Then I am mad that I didn't write it down.
A paradox of sorts, and very annoying.