President Barack Obama offered a final thank you to the American people Thursday in a goodbye letter.

In the letter published on the White House website, Obama credits U.S. citizens for being a "source of goodness, resilience, and hope" as he faced trying times during his presidency.

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"Throughout these eight years, you have been the source of goodness, resilience, and hope from which I've pulled strength. I've seen neighbors and communities take care of each other during the worst economic crisis of our lifetimes," Obama wrote on the eve of Donald Trump's inauguration. "I have mourned with grieving families searching for answers -- and found grace in a Charleston church."

He continued:

"I've taken heart from the hope of young graduates and our newest military officers. I've seen our scientists help a paralyzed man regain his sense of touch, and wounded warriors once given up for dead walk again. I've seen Americans whose lives have been saved because they finally have access to medical care, and families whose lives have been changed because their marriages are recognized as equal to our own. I've seen the youngest of children remind us through their actions and through their generosity of our obligations to care for refugees, or work for peace, and, above all, to look out for each other.

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I've seen you, the American people, in all your decency, determination, good humor, and kindness. And in your daily acts of citizenship, I've seen our future unfolding."

Looking to the future, Obama pleaded with the American people to join together to achieve "progress."

"And when the arc of progress seems slow, remember: America is not the project of any one person. The single most powerful word in our democracy is the word 'We.' 'We the People.' 'We shall overcome.'

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Yes, we can," he wrote.

Obama's letter comes a day after the first lady posted a short video on Twitter of her stroll through the White House. In the clip, Michelle Obama was accompanied by the beloved family dogs Bo and Sunny.