Every relationship, romantic or otherwise, is built on a foundation of trust. The closer you feel to someone, the more likely you are to share secrets and even unsavory moments from your past, because you can trust them. Dr. Abigail Brenner, a clinical psychologist, discussed traits of partners and best friends with Psychology Today, saying, "you openly discuss everything—the good, the bad, and the ugly." In other words, nothing is hidden.

Though it's normal for the rush of teenage lust to fade a bit in a relationship, if you've found that your partner still gets you all hot and bothered, it's probably because there's a solid friendship underneath. Dr. Jane Greer, a relationship expert told Women's Health, "if you meet someone and have chemistry right away but don't build a friendship, that passion will run out because there's nothing to support it."

Sometimes the best part about dating your best friend is that you don't even see labels at all. There's no line showing where friendship ends and a relationship begins; it just blends together. "It’s more about that social relationship than the legal status," psychologist Bella DePaulo told The Huffington Post. "Marriage, in a sense, is a super friendship.”

If you've got two tickets to a show, want to try out a new restaurant, or have been thinking about going on a road trip, chances are, your significant other is the first person you though of to accompany you. You know you're on the best friend level when you're each other's first choice for any kind of adventure.

Life doesn't have to be rainbows and unicorns 24/7, but if life with your partner is pretty damn good for the most part, your SO and your BFF are one in the same. Isadora Alman, a marriage and relationship therapist, told Psychology Today that "two people who each have their needs met will make much better and more interesting partners to each other." So if you're feeling good about things, you're doing a great job of meeting each other's needs in the friend and lover departments.

My favorite thing to do with my husband might sound boring to most, but we love it. Once our son has gone to bed, we just hang out on the couch, watch TV, joke around, and it's great. If you can do, essentially, nothing with the person you're dating and still have a good time, you've hit the BFF jackpot.

According to a recent study from the University of British Columbia's Vancouver School of Economics conducted by researchers Shawn Grover and John F. Helliwell, couples who consider their partner their best friend get almost twice as much additional life satisfaction from marriage or co-habition as others do.

Feeling like you can truly depend on your partner, the same way you'd turn to a reliable friend in a time of crisis, is a huge sign that you're dating your best friend. Dr. Robert Waldinger, a psychiatrist and Harvard professor, told The New York Times that dependability is key, saying "people who fared the best in life were the people who leaned into relationships with family, with friends and with community."

The same way a friendship goes downhill quickly because one person is more invested than the other, a relationship fares the same. If you're actually dating your best friend, you'll know because you both put in equal effort. Brenner told Psychology Today, "each of you contributes your fair share to the relationship. Each partner brings their best strengths and abilities for the benefit of the 'team.'"

You might think this goes without saying, but it's important that you like who you're dating. Lust can fizzle and love is nice, but at the end of the day, if you can't have fun and kickback with your SO, you're not BFFs. So if you like and love who you're dating, you've won the best friend soulmate lottery.

My grandparents on my father's side had one of the most beautiful, loving relationships, but there was one thing they were divided over: football. She was a die-hard Florida State University fan and he loved the Gators. So how did they still act like best friends after decades of marriage? Because they agreed where it mattered. Greer told Women's Health, "when you have the same outlook on relationships, it shows that you share similar values and want the same things in a partnership."