On Wednesday, Donald Trump will cease to be the American president. Though I don't want President-elect Joe Biden to be our chief executive, I won't pretend I'm anything but glad to see Trump go.

Yet I also can't pretend I've haven't learned from Trump. He has dominated our national public life to an unprecedented degree and, in the process, served as an exceptional negative object lesson. And the chief lesson, for me, is this: You can't compartmentalize character.

Lack of self-discipline in one part of your life will not stay contained. Habitual dishonesty won't be isolated to a single relationship or role. Tacit approval or utilitarian cooperation with deceit and corruption will have unintended consequences. A little yeast leavens the whole batch of dough.

Sometime before the Trump era — maybe 2013, though I don't remember exactly when — I have a vague recollection of rehashing the old character vs. policy debate with some colleagues. We were all libertarians, which meant we had little hope of finding a politician with a national profile and electoral viability whom we could wholeheartedly support. So the question of our conversation was: Should we take whatever we can get? If presented with a candidate who paired (in our view) perfect policies with a disreputable personal life (back then, former President Bill Clinton was the prime example), is that the best we can do? Should we make the bargain?

I can't recall exactly what I argued, but I know it was equivocal. Conscience wouldn't let me say character was irrelevant, but the idea of a political standard-bearer was so appealing. Think of the good that could be accomplished! The wars that could be ended! The injustices righted! It would be preferable, of course, to have someone personally ethical lead the way. But was it necessary?

I wasn't sure then. I am now. It is necessary.

Trump has shown, over and over, that dysfunction and wrongdoing in one part of life will migrate. Consider the tweets. "I just wish he'd tweet less" was a regular refrain of Trump's more ambivalent voters — the ones for whom "owning the libs" had not become an end unto itself — particularly during the first half of his presidency. The sentiment is understandable, but it relies on the false assumption that silencing the tweets would make a whit of difference to who Trump is. His Twitter use undoubtedly helped shape his character, but take away the tweets — as Twitter did this month — and Trump will not cease to be the sort of person who would think and say those things.

The tweets are but one example of so very many. Trump has shown that a man who will betray his wife (and his next wife and his next wife) will betray his political partners, too. A man who will lie about small things that don't matter will lie about big things that matter very much. A man who has no self-control in his own routine — who is regularly awake and rage-tweeting at 3 a.m.; who spends hours and hours absorbed in cable news; who in the twilight years of his life still hates to eat his vegetables — will not magically develop discipline when he turns his attention to weightier concerns. A man who has spent decades nursing grudges, seeking revenge, and refusing to admit when he is wrong will not suddenly change his ways when tasked with far more important work than playing himself on television.

The phenomenon I'm describing here is in no way unique to Trump. It is true of all of us: How we live gradually determines who we are. The habits we make are formative. "At 50," George Orwell wrote in a private notebook shortly before his death, "every man has the face he deserves." That evolution isn't always as neatly correspondent in reality as it can be in fiction, but the notion that our choices pile up to make our selves is true. Trump has provided a daily demonstration of it these past five years. He has become a warning, a signpost of where not to go, how not to age, what not to become.

The most immediately pressing part of that warning, to my mind, is learning how to self-regulate our internet content consumption, especially the political content. (I say this to myself as much as anyone else.) Over the course of a decade, Trump went from posting an average of one tweet every five days to about 35 tweets daily. He tweeted lies, insults, conspiracy theories, fantasies of violence, and reactions to live television. Twitter's permaban stopped that output — but absent massive (and massively unconstitutional) new regulation of the internet, no law or tech company can stop the content intake that fueled it. That is a choice only the individual internet user can make.

Few of us have an online output as noxious as Trump's, but we all must learn to regulate our intake. I'm not sure we'll preserve the fragile bonds of society if we don't. I'm not sure we'll preserve our souls.