3 reasons your friendship feels 'toxic' — and what you can try before breaking up

• Close friendships can sometimes feel toxic without you knowing why.
• Author Danielle Bayard Jackson said there are 3 areas that matter in female friendships.
• Strong friendships feel equal, exclusive, and mutually supportive.

Becoming best friends can feel a little like falling in love. You click immediately, cracking jokes like you've known each other for years. Opening up to them is as natural as breathing, because you don't have to explain so much. They just get you.

It's a beautiful experience, but one with under-appreciated complexities, Danielle Bayard Jackson, an author and friendship coach, told Business Insider.

Strong friendships have three core tenets: symmetry, secrecy, and support, Jackson said. If one area feels off, it creates tension in the relationship.

In writing and researching her book, "Fighting for Our Friendships" (out on May 7), Jackson found these principles are especially valued in female friendships. "I'm not saying that men don't value those things, but I'm saying women prioritize them more," Jackson said. "It's going to be a dealbreaker for us if those things aren't there."

It may not be that your friendship is rotten, it may be that one of these areas of your bond is off-kilter.

So before you dub your bestie a toxic friend, here are three major reasons your relationship feels like it's on the rocks — and what you can try before quiet-quitting the friendship.

1. You don't feel like equals

According to her research and personal experiences, Jackson said that "wanting to feel like things are equal is one of the top grievances women share about their friendships."

Many things can throw off that sense of symmetry or alignment. You might feel that your friend is jealous or competitive with you, making subtle jabs that put you down. Or you may believe the friendship is one-sided: you initiate contact most of the time, or notice your BFF is an energy vampire who never asks you questions. In her book, Jackson offered ways to start conversations around those issues, as well as advice on when to just walk away.

But sometimes, imbalances can be more innocuous: being in different life stages can switch up your dynamic, too.

In the book, Jackson said that "it's important to identify other ways you two are similar" if you feel like the interests that bonded you are rapidly changing. If your friend you always went to happy hour with is now sober, find new activities you can do together. If you have kids but your BFF is a DINK, look for other ways to relate to them.

2. You question how close you really are

"Secrecy" is the second big area that threatens female friendships. In the book, Jackson described close friendship as creating a "vault" where "each friend contributes private things in an intimate and trustworthy space."

Beyond the ability to keep secrets, Jackson said it's also important that both friends reciprocate the depth of sharing.

You might have a friend that you would call first if you got engaged or a promotion at work. But "if I feel like she's telling other people big milestones before she shares with me, I'm going to start to have tension," Jackson told BI.

If your friend doesn't share as much as she used to, or talks about the same deep topics with other friends as she does with you, it makes you unsure of how close you actually are.

Jackson said this doesn't always mean your friend is at fault: for instance, if you feel jealous of their new work wife, it can actually be a healthy motivator for continuing to be a good friend to them.

3. You don't feel supported enough

Based on her research, Jackson told BI that "emotional support is the number one thing women look for in their same-sex friendships."

It's also one of the trickiest areas to navigate, because "we're not often articulating what support looks like," she said. "We assume that other women just know."

In one example from the book, you might view support as a friend buying something from your new online mug store. But to your friend, linking your Etsy shop in an Instagram story is ample support.

Just as in healthy romantic relationships, Jackson said you can't expect your friends to adequately know how to support you if you don't share what that means to you.