I bought Marvel Enterprises- MVL - the comic book company around 19-20 and sold around 24. When the stock went up to 29 I figured I had misjudged...
The first time I wrote this, I typed "...I misjudged" but I decided "I had misjudged" was better. Of course, if I had been speaking there would have been no time for me to change my words. I think that past simple (I misjudged) can usually substitute for past perfect (I had misjudged) in casual language use.
Feel free to respond with your own examples or start a new topic to discuss different grammar. More on the past perfect:
Past perfect "Arlo Guthrie" class from ESL go.com
Past perfect "Obong mountain" class from ESL go.com