I’ve become afraid of keeping thoughts in my head

Has this happened with you before?
You think of something.
You are not able to act on that something, in my case write it down somewhere.
And then, you forget about it.
Or, the idea itself does not seem that great after a while. You lose the passion for the idea.
Or, you forget what it was that you wanted to write in the first place.

I had an idea in the morning today, mostly about what I wanted to write as an acknowledgment for my book.

And I found myself wanting to get on the Mac and type it down. Right then and there. I was afraid I would lose it, this thought.

And I thought, why am I so afraid to keep this thing in my head. Is it so feeble, that if I not right it down this very second, I would lose it? And if it is so feeble is it any good?

I do not work things over in my head anymore. I do not exercise that muscle anymore. I think on paper, while writing. I do not know if it is good or bad. It just is.

I have this appendage that I have exported my thinking to, my phone. This was not how it was earlier, and yet, I was able to think and work on the thought in my brain, till it was ready to be on paper.

I need to exercise that muscle more.