Former first lady Michelle ObamaMichelle LeVaughn Robinson ObamaObama: 'Hopeless' to try to sell as many books as Michelle Obama sold record-breaking 1.7 million copies of memoir in first week Media and Hollywood should stop their marching-to-Georgia talk MORE on Tuesday revealed one phrase that was on her mind on the day of President TrumpDonald John TrumpPennsylvania Supreme Court strikes down GOP bid to stop election certification Biden looks to career officials to restore trust, morale in government agencies Sunday shows preview: US health officials brace for post-holiday COVID-19 surge MORE's inaugural, also the day she and former President Obama left the White House.

"Bye, Felicia," Obama said Tuesday on "The Tonight Show Starring Jimmy Fillon" as Fallon held a photo showing Obama and her husband boarding a plane following the inauguration.

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“A lot was going on that day. That was a day," the former first lady added.

Obama told Fallon that she is optimistic about the future of the country because of the young people and says older generations owe the younger ones that "hope" and "optimism."

"Everywhere I go, I get to see young people. And we owe young people that optimism, that hope, because what’s the alternative? And they come into this world ... with so much promise," she said.

Obama is currently on tour promoting her new memoir, "Becoming."

The book quickly became the best-selling book of 2018 following its release last month and has already sold more than 3 million copies.