Allan, this is what I was thinking.
Here is another example.
I am trying to remember someone's name and it is driving me crazy because I have gone blank and can not remember it. In this situation, I find the best thing to do is stop trying to think about it, let it go and do something else. Later on out of nowhere the name will come to me.

I apply this approach to the fretboard. If I'm trying to create a new tune and I can not find anything interesting, I let it go and come back later. Somehow when I'm not thinking about it, it will come to me.

Banjo Bonnie