How to Be a Human

The beauty of being human is that we are incredibly, intimately near each other, we know about each other, but yet we do not know or never can know what it’s like inside another person.
~John O'Donohue, poet, theologian and philosopher; author of Walking in Wonder: Eternal Wisdom for a Modern World

Among the worst is the unknowingness. We were so sure, weren't we? We were certain that this man with whom we made vows would never betray us. So when he's revealed to be someone capable of something we thought him incapable of, it frightens us. It calls into question everything we thought to be true, everything and everyone we trust. We stare into the abyss. 
Yet what's revealed when we learn of a partner's betrayal is something that was always true: "...we do not know or never can know what it's like inside another person". 
That was true the day we took our wedding vows. It's true on D-Day. It's true today.
What's also true is that we don't fully know ourselves either. Learning who we are is our life's work. 
Most of our unfaithful husbands are as shocked at their behaviour as we are. There's a famous (and famously unethical) psychological study – the Milgram experiment – in which people believed they were doing harmful things to others but continued because an authority figure was directing them. 
I'm no longer convinced by anyone who insists they would "never" do something or that they are certain they would. Most of us don't know how we'll behave in a situation until we're in that situation. 
Case in point: Did you think you'd stay in a marriage if your partner cheated? I thought I'd be outta there in a hot minute. Yet, here I am.
Part of staying in my marriage meant accepting the frightening truth that I hadn't really known my husband. Not completely. I knew him, of course. I knew that he was practical rather than frivolous. That he worried about growing old. I knew that he loved dogs and tolerated cats.
What I didn't know, in part because he hadn't yet admitted it to himself, was that so much of the pain of his childhood drove behaviour that was inconsistent with his stated value system. How to reconcile ourselves to someone who believes in his own decency yet betrays his wife and treats sexual partners like objects? 
It's only by acknowledging these contradictions – in others but also in ourselves – that we have any hope of truly knowing others and knowing ourselves. As long as we're willing to pretend the shadows don't exist, we're lying to ourselves. As long as we think we absolutely know another's heart, we're lying to ourselves.
So...where to go with that?
We embrace the beauty of being human, which is to say, we embrace the beauty of imperfection, of flaws, of screwing up. We do what we can to keep our hearts open. To learn to love our own flaws even as we attempt to soften them, to file off their sharp corners. 
Accepting others' humanity is not the same as accepting their poor treatment of us. That's where boundaries come in – to remind others that they are either free to respect our boundaries or to take their circus elsewhere. It starts as an inside job – with learning to go easy on ourselves for our imperfections. (My beloved Mary Karr puts it this way: "It’s not like I’m not an asshole—people know the ways I’m an asshole and it’s within the realm of acceptable asshole-ocity.") And when we're able to do that, it becomes a default setting. We are easier on others. We don't tolerate toxic behaviour (boundaries again!) but we learn to live with the various ways we all kinda assholes. 
My husband is a sex addict. Even though he no longer acts out, I cannot pretend that his addiction isn't there. What I can do is accept that truth while realizing that I don't know what that's like for him. Perhaps I will never know. And there are undoubtedly other secrets he holds, secrets he's still discovering. 
As I continue to discover my own. As long as we're scared of our secrets, they control us, whether consciously or otherwise. (We're only as sick as our secrets, right?)
O'Donohue notes that "we know about each other". He doesn't say we "know" each other. Because we will never fully know each other. We will never fully know what it feels like in another's skin. We'll be lucky if we die fulling knowing ourselves.
It's contrary to everything we've been taught about love, isn't it? That love is "you complete me". That love is "soul-mates". "My other half." 
I regret to inform you that it's none of that. 
Love is choosing to figure out who you are alongside someone else working to figure out who they are. Love is choosing to fix your broken spots alongside someone else who will support you in doing that. Love is believing that life with this person, even in his brokenness, is preferable to life without him. 
The beauty – and yes, the challenge – of being human is the unknowingness. And opening our hearts to it anyway.