If you are blessed by a good thought, do not hesitate to write it down at once. Good thoughts are visitors from Elsewhere and like most visitors they do not like being snubbed or made to wait.
Let us say a fine aphorism flashes before your mind. There it is is fully formed. All you have to do is write it down. If you don't, you may be able to write only that an excellent thought has escaped.
"But there is more where that one came from." No doubt, but that very one may never return.