It is easy for me to see your “foolishness” (folly NASB) (200). You are the first one I picture when I read verses like this. I would venture to guess that if you knew me you could see how obvious my shortcomings are. We are always good at seeing where others could do better. The problem we have is in seeing our own foibles.
This is another place where we see the principles of the Old Testament taught by Jesus in a way that people think is new. Here Solomon is saying that silly pastimes are wrong even when we are just thinking about them. Jesus may have had that in mind when He was teaching.
(Mat 5:27-28 KJV) Ye have heard that it was said by them of old time, Thou shalt not commit adultery: But I say unto you, That whosoever looketh on a woman to lust after her hath committed adultery with her already in his heart.So? Guard your fantasy life and flights of imagination. God wants to be Lord there too.