Sometimes you know what your SO needs before they even realize it. "You intuitively know what each other needs. There's a high degree of empathy and empathic connectedness (awareness and understanding), almost to the point of being able to read their mind," as licensed therapist Dr. Santan tells Romper. You know exactly how to brighten their day, even if it's as simple as going on a coffee run.

It's kind of a cliche, but there's some truth to the idea. If you and your SO can finish one another's sentences, then you're pretty well connected, says Dr. Santan. Finishing one another's sandwiches is a good sign, too.

A little distance is no big deal. "You're comfortable with time away since you know that you are meant to be together," says Dr. Santan. It isn't necessary to spend every waking moment together.

Do you and your SO take pics you'd never post? "If the two of you are able to go way back in time with your ugly selfies together, you know you’ve got a good thing going," says health & wellness expert Caleb Backe of Maple Holistics. "There’s a certain stage in a relationship where those double chins and pimple-filled photos are taken, so if you’re starting to gather a collection then you might well have found your soulmate." It proves you're super comfortable with one another.

Arguments are just a normal part of relationships. "Being able to take your fights lightly proves that you’re comfortable with each other and that your communication is open enough that you know you’re not really offending one another," says Backe. Plus, cracking a few jokes is the best way to ease tension after a disagreement.

Sometimes things just get real in relationships, and that's totally OK. "If you can spend time with your partner whilst sporting a big white zit on your face and not feel self-conscious about it, the two of you are destined to be," says Steve Phillips-Waller, founder and editor of lifestyle website A Conscious Rethink. It's a surefire way to show you're super comfortable.

That super cutesy, super embarrassing way you speak to each other is actually a good sign. "It’s pretty much instinctive to talk to loved ones the way our first loves (our mothers) spoke to us," said professor Dean Falk in The Cut. "The musical part of baby talk (a.k.a. ‘musical speech’) is largely a product of the right sides of our brains and conveys affect or emotion, just as music is sometimes called ‘the language of love.'" Yes, even those pet names you'd never speak in public count, too.

A partner's clothes are always more comfy than yours. In fact you might even forget that sweatshirt was your SO's first, as noted in Buzzfeed. Merging closets is just part of merging your lives together.

I'm so glad other couples do this. As it turns out, plenty of couples have songs they make up just for the pets, according to Cosmopolitan. It's a fantastic way to make each other laugh, too. Honestly, just try singing "kitty cat in the sky" to the tune of the "Reading Rainbow" theme without cracking up.

If you're tempted to fix your SO's hair or brush some lint from their shirt, it's all part of couplehood. As it turns out, trying to groom your partner is a natural instinct, according to Bustle. Just don't share toothbrushes and it's all good.

No, not the sexy kind of shower. Longtime couples can take regular showers together, according to Lifehack. You just enjoy one another's company that much, and it can save a little water in the process.

Once you know someone well, it's so easy to be irritating on purpose. In fact, plenty of couples deliberately annoy one another, whether that's by mispronouncing words or tickling, according to Life. Few things are more fun than making your SO squirm.

When you're with someone you really trust, then it's time to order what you really want from the menu, even if that's the BBQ plate. Hey, eating messy food in front of your SO means you're pretty close and comfy, according to Bolde. Plus, you should feel free to enjoy your favorite meals.

At some point, couples feel comfortable saying just about anything to each other. For instance, you might ask the partner whether they've showered recently, as noted in Elite Daily. It's the sort of thing you would probably never dream of asking a first date.

Now this is a sign of true love. It's even better if you just bring the whole pizza box into the bedroom too.

At some point, nudity is the norm. "It’s not even sexy; it’s just practical and comfortable," said relationship and dating expert Jonathan Bennett in Bustle. So embrace the no-clothes Netflix time.

For people who enjoy delivering sick burns, there's no better target than your SO. In fact, couples who enjoy being laughed at tend to have higher relationship satisfaction, according to a study in Journal of Research in Personality. As long as everyone is just having fun, these playful taunts can add a little spice to your relationship.

OK, so you could call it laziness. But texting your SO from another room (or even the same room) is pretty common, according to HuffPost. Hey, sometimes you just don't feel like getting up for your own snacks.

If you and your partner can discuss silly secrets, then this shows you're pretty close. Trusting your SO is worthy of these secrets is a positive sign for your relationship, according to Refinery 29. Plus, how many other people know you carried a torch for Jonathan Taylor Thomas back in the day?

Don't overlook the Netflix half of the Netflix-and-chill duo. "Watching television with others provides a place of common experience: shared ‘show lingo,’ inside jokes, and an easy way to be together without the demand to create your own entertainment or conversation," said social confidence coach Jenna Purcell in Rewire. It's an easy way to bond.

Couples who laugh together have staying power. "If you share a sense of what's funny, it affirms you and affirms your relationship through laughter," said communications studies researcher Professor Jeffrey Hall in Business Insider. Whether you're laughing at each other's silly jokes or speaking a cutesy couple's language, these are the weird behaviors that can bond partners for life.