Dean Obeidallah, a former attorney, is the host of SiriusXM radio's daily program "The Dean Obeidallah Show" and a columnist for The Daily Beast. Follow him @DeanObeidallah. The opinions expressed in this commentary are his own. View more opinion articles on CNN.

(CNN) You could write an encyclopedia about the ways in which Barack Obama is different from his successor, Donald Trump. On Saturday, Michelle Obama provided a more concise explanation for what distinguishes the two presidents from one another: Obama put country first; Trump puts himself first.

The former First Lady, while speaking at an event to promote her new book, "Becoming," explained the genesis behind the line she famously delivered at the 2016 Democratic National Convention: "When they go low, we go high."

As Mrs. Obama explained, "That motto is his motto," referring to her husband. She continued, "I say that because that's how Barack operates," adding, "I mean there's so many times when I just want him -- like I know all of you -- to just curse them out ."

So why didn't her husband go full Trump as president and personally demean and ridicule his opponents on social media and at rallies? As Mrs. Obama explained, the reason why a person would go "low" is simple: "Oftentimes, going low means you're acting from a place of ego. You're really just satisfying your immediate need to lash out."

Then she shared two key lines that summed up her husband's guiding philosophy on why he avoided going "low" in response to his critics: "The president isn't the president for his own ego. The president is the president for the entire country."