Yesterday morning I woke up with a song on my mind, and that I did not get out of my mind until I got so busy with other things that it finally faded away. This morning I had to think a minute or two to recall what song it was! It was a song with the words "I have returned to the God of my fathers, to the same simple faith, as a child I once knew..." This was once a popular song, though it wasn't particularly among my favorites. But I suppose I heard it quite a bit on the radio.
So with no rhyme or reason I woke up with a song on my mind that I had not thought of in years, and wouldn't have had a reason to think of. Yet it was there, racing through my head and back again, over and over.
The human mind is an amazing, and peculiar, thing. Things like this song, instant recall of something by a crossword puzzle clue, and other experiences tell me that whatever enters the mind is in their somewhere, even when we don't know the "buttons" to push to recall something we want to remember.
One significance is that we ought to be careful what we put in there, because it is there to stay, for good or evil. One way to counteract the evil stored therein is to "let this mind be in you, which also was in Christ Jesus..."