It's a long-standing tradition for the sitting president of the United States to leave a parting letter in the Oval Office for the American elected to take his or her place. It's a letter meant to share what we know, what we've learned, and what small wisdom may help our successor bear the great responsibility that comes with the highest office in our land, and the leadership of the free world.

But before I leave my note for our 45th president, I wanted to say one final thank you for the honor of serving as your 44th. Because all that I've learned in my time in office, I've learned from you. You made me a better President, and you made me a better man.

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.

I have mourned with grieving families searching for answers – and found grace in a Charleston church.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.

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.

All of us, regardless of party, should throw ourselves into that work – the joyous work of citizenship. Not just when there's an election, not just when our own narrow interest is at stake, but over the full span of a lifetime.

I'll be right there with you every step of the way. 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.'

Yes, we can.