There is a special milestone in each significant relationship that is rarely celebrated. There’s no holiday, no dinner, and no party. It just happens – one day you’re strangers, the next you’re not.

It’s the day you hand over your passwords to your SO.

Everyone reaches this particular milestone differently. Some – if they’re smart or particularly untrusting – never reach it at all.

Sometimes people realize one day, without ever being told explicitly, that they already know their partner’s passcode. Some treat it like a small declaration of trust and intimacy. “0852,” they say, proudly. “Don’t snoop.” Others learn out of circumstance. “Can you text Jane and let her know we’ll be late?” they ask with their hands full. “My phone is over there. 4928 is the passcode.”

And then it’s happened. Likely the two most important entities in your life, your partner and your smartphone, are bound together. They have access to each other. As with any new phase, if this milestone is reached too early it can spell trouble.

A couple years ago, I started dating a girl named Rosie. We had both just gotten out of serious relationships, and the rebound factor was clouding our judgement. That said, we moved way too fast. After a month or so of dating, I was essentially living at her place. I had a set of keys. We were grocery shopping together and combining laundry. (I’m a cliche, I know.)

I remember when I eventually gave her access to my digital world. I was making meatballs, and she asked me to send her a picture I had taken earlier that day. Hands covered in raw hamburger meat and egg, I said she could do it herself: “9873.”

She smiled, silently accepting my trust. It was an offering I made out of circumstance, but I also can’t pretend that I didn’t quietly warm up at the notion of being that close to somebody. And make no mistake, it’s a unique type of closeness that can’t be achieved through passionate sex or honest conversation. Your smartphone is a reflection of yourself. It knows more about you than almost anyone. Your entire history, from years worth of communication and pictures to general interests, is recorded right on the device.

Eventually, we grew even more “trusting” with our digital lives. We left our computers open, email and Facebook logged in, and didn’t worry about snooping or invasion of privacy with each other. It wasn’t a conversation we had, but as trust grew in the relationship, we simply left more things accessible in the digital realm.

For a minute there, I actually believed that this form of sharing strengthened whatever trust we already had. I had opened myself up to her, and she to me.

But that ended.

After we had been dating about six months, I got a call while I was on a business trip in Atlanta.

“How much did you spend on the flowers you bought Hayden?” she asked coldly.

Hayden was my ex, and when Rosie and I first started dating, I had sent Hayden flowers to congratulate her on a new job. Rosie knew about it, but I might have lied about how much I had spent.

“Like… $30,” I said, sticking to my lie. Meanwhile, I was frantically flipping through my phone to figure out how she knew I had lied.

“You left your email open on my iPad, Jordan,” she revealed. “I’m looking at the receipt right now. So did you still only spend $30?”

That fight lasted all night. We moved on eventually but the breach of trust on both sides of the relationship never left. And by that point, there was no way to go back. I couldn’t very well change all my passwords. She had already caught me lying. Any new password that shut her out of my life would be a red flag, signaling that I was lying or misbehaving once again.

Though this story is my own, I’m certainly not alone in the password swap or the snooping significant other.

In fact, teens seem to think of password sharing as a modern-day equivalent of exchanging letterman jackets or senior class rings. The NYTimes found that around one in three teens has shared a password with a boyfriend, girlfriend, or best friend, with girls offering up the secret spell more often than boys.

I talked to my sister about it. She’s 21, and goes to a state university in the south. And just as I have a different perspective from people who didn’t go to college with Facebook, the divide between us is bigger than five years suggest. She had Facebook, and an iPhone, from the age of 13.

“I know a girl — this is really creepy — but I know a girl who wanted to know if this boy she was crushing on sent just her a snap, or if it was a mass snap he sent to a bunch of people,” she said.

“She went on and checked his Snapchat score to see if his points had gone up for more than one person. Creepy, right?”

She said she has another pair of friends who have been dating for a while and have a policy in place: they know each other’s Facebook and email passwords at all times. To me, having a “policy” regarding sharing passwords is even creepier than Snapchat score stalking.

Between 30 and 40 percent of adults over 18 have snooped on the call history or the email of a spouse or partner.

Between 30 and 40 percent of adults over 18 have snooped on the call history or the email of a spouse or partner, according to a 2011 study.

In the UK, it’s even worse. A 2013 survey shows that 62 percent of men and 34 percent of women admitted to looking through a partner’s phone without their knowledge, and more than half of them already had the passcode they needed to conduct their spy work.

Almost all of them said their reasons for this were based around jealousy and insecurity, and they were checking to see if any infidelity had been committed. Sadly, about half of them had their suspicions confirmed — their partner was cheating. The evidence usually surfaced in text messages or through direct Facebook messages.

It seems to be a much bigger issue for younger couples, but that doesn’t mean that older folks are excluded.

Michael, a friend of mine who is married with three children, and pushing 40, says he sometimes checks up on his wife’s email or phone.

“I go through her Gmail about once a year,” he told me. “It’s not with any intent, and I never expect to find anything. I trust her, but it just kind of happens.” But Michael believes we, the younger generation, have it much worse. “You think social media is a reflection of the person, when really it’s a reflection of a reflection,” he explained. “Making a big deal out of your boyfriend friending his ex is stupid. Unless he’s actually cheating on you, it’s harmless.”

Perhaps he has a point. Studies show that simply being on Facebook breeds more jealousy in a relationship.

And maybe, when I’m older and wiser, I’ll feel differently about how much of me — the real me — is exposed within my digital imprint. But right now, my smartphone and its contents don’t feel like a reflection of a reflection. My thoughts, hopes, dreams, interests, secrets are all in there. It’s the piece of my mind that I carry in my pocket instead of inside my skull or inside my chest.

But right now, my smartphone and its contents don’t feel like a reflection of a reflection. It’s the piece of my mind that I carry in my pocket instead of inside my skull or inside my chest.

A few months after the flower fight, Rosie and I were laying in bed after an incredibly long day. I was starting to doze as she played a game on my phone. I woke suddenly to her voice.

“What is this?” she said, holding a bright phone screen in front of my sleepy eyes. She had found old correspondence between Hayden and I in my text messages.

“Why are you reading my texts?!” I said angrily.

“WHY ARE YOU TEXTING YOUR EX?!” she snapped back.

The relationship didn’t end then. We went on to torture each other in new and interesting ways for another six months. But whatever future we had came to an end that night. The milestone of sharing those passwords, whether by accident or circumstance or with the intent to “share everything,” came far too early. It came before actual trust had been established. We mistook the symbolism of trust, embedded in those passwords, as actual trust.

Because Rosie and I weren’t ready — after all, I was texting my ex and lying to her — the exchange of passwords only made things worse. Whatever small amount of trust there was easily abused. It wasn’t enough to resist the temptation of my open email account and un-holstered smartphone. And once she crossed the line, I didn’t trust her with that temptation anymore, either.

“I wouldn’t be half as mad if someone went through my drawers and cabinets and shit,” my friend Carrie Anne said in a text. “I wouldn’t even be as mad if they read my diary. But with texts and emails, it’s such a condensed and far-reaching invasion of privacy, and my friends’ privacy, and my employer’s privacy.”

But snooping seems to be a temptation many people can’t withstand. And maybe that’s the technology’s fault.

“Kids these days don’t know how to sneak around,” said my friend Jessy. “They don’t know how to really be dishonest.”

I’m told there was a time, before the age of the internet and even cell phones, that cheaters had to do quite a bit of sleuthing to get away with an affair.

“You had to find someone outside your normal circle, and be an excellent liar, and hide your credit card statements,” said Jessy. I followed her train of thought, and realized how incredibly difficult it must have been to plan out an affair without your own smartphone, or an email account. The most obvious answer is to use work phone lines only. What a closed world it was when you weigh it against our various cheating channels today.

“And if your partner is fooling around on you, you had to do even more work,” Jessy said, recounting the story of when she found her ex-husband’s phone records with a woman in another state. “You had to be able to tell they were lying, and then rely on your gut to confront them. Or else just follow them around town.”

In today’s world, a quick glance into someone’s smartphone tells you everything you need to know. From there, you can access email and call logs and Facebook and text messages and Tinder and photos and anything else that might be incriminating. The same channels we open to each other, as a sign of trust or love or intimacy, are the very ones we’re most likely to cheat on. No wonder snooping is so popular.

If you have access to every potential method of cheating, then you have no reason not to trust your partner, right?

And no wonder exchanging passwords feels so much like real trust. If you have access to every potential method of cheating, then you have no reason not to trust your partner, right?

Unfortunately, it’s not that simple.

Sharing passwords may be a symptom of trust that already exists between two people, but it cannot be proof of that trust. It cannot be the reason there is trust. When it’s real, those passwords aren’t actually needed. They may be convenient, and they may be a great safe-guard for married couples (just in case something tragic ever happens), but they are not a required clause in the trust treatise.

That’s not to say sharing certain passwords is a bad thing. The phone password, at a certain point, almost always becomes fair game in a trusting relationship. Dating and married couples use each other’s phones — it just happens.

But email and Facebook are different.

Sam Biddle put it well in an old Gizmodo article: “The inbox is one of the few sacred places left online, the only space on your monitor not shared into oblivion. This isn’t about having something to hide—it’s about keeping meaningful boundaries in an era when there are verrrrry few. We all need whatever scraps of privacy we have left, and your email is just that.”

Privacy is just as important to a relationship as openness and honesty. Not everything that needs to be said needs to be heard. And, in a way, my friend Michael is right: Not everything that happens on a person’s smartphone or in their inbox is an accurate portrayal of their loyalty.

Context, by definition, grants access to true understanding. And in the context of snooping through your partner’s digital life, everything you see is out of context.

The message from his or her ex, or the cordial response back, or the pictures stored from past relationships all seem like direct attacks on your happiness. They are not.

When I sent Hayden flowers, I lied about the price because I knew Rosie was sensitive about my ex. I didn’t send Hayden expensive flowers to win her back — I was actually really happy with Rosie and wanted to pursue the relationship. But to Rosie, the lie and the cost of the flowers signaled otherwise.

We trust that the ones we love won’t leave us, won’t cheat, won’t run. But that trust used to come from inside us. When love can be reduced to a four digit passcode or a swipe through an email list, that trust is cheapened. Mark Twain said we’re like the moon – a light side and a dark side we show no one. Nothing on our phones is particularly dark, but it certainly is private.

#Love is a new column on TechCrunch dealing with digital matters of the heart. It explores our relationships, their relationship with technology, and all the gory details that come with it. I will be leading the charge, and am looking for guest writers to tell their own stories each week. Maybe you found your soul mate on Tinder, or got dumped on Facebook, or have an outrageously interesting sext life. We all have our stories. If you’re interested in contributing, send an email to jordan@beta.techcrunch.com with the subject line #Love for more details.