What if, the next time somebody hurt your feelings, instead of getting defensive or trying to change their behavior, you just… let them?

That seems to be the ethos on TikTok, where videos tagged #letthemtheory have accumulated 30 million views.

Credited to podcast host, author and motivational speaker Mel Robbins, the "let them" theory goes something like this: Instead of getting upset at other people's actions or trying to control their behavior, just let them do what they're going to do − and don't take it personally. For instance, all your friends hanging out without you? Let them. Your significant other can't commit and wants to breakup? Let them. Your company's having layoffs? Let them.

The goal of the theory is not to change a negative outcome that's beyond your control but to let go of expectations, anxiety and resentment that could weigh on your mental health.

"You spend so much time and energy trying to control other people and getting emotionally worked up about things that are beyond your control," Robbins says in a TikTok with 1.7 million likes. "You can tap into peace and true control if you let them be themselves."

She adds: "If you 'let them,' people will then reveal who they truly are, and, when they reveal who they truly are to you, you now know what you can choose next that's right for you."

Experts say there's a lot of utility to this mindset − but there are other important things to keep in mind as well.

"It's a great strategy, and what's interesting about it is that the whole basis of it, or a big part of it, is to let go of control," mental health counselor Catherine Del Toro says. "In this struggle of trying to control an outcome, if I let them do whatever they want to do, then I have a part of that outcome as well."

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It's OK to 'let them' while also feeling your feelings

The "let them" theory is great for letting go of control and reclaiming a sense of power in how you respond to things.

It can't, however, totally erase the hurt someone caused you, even if you accept that it's not your fault and there's nothing you can do to change them.

Psychologist Stephanie Sarkis says it's important to give yourself permission to feel your feelings, even while embracing a "let them" mentality. After all, saying "let them," while the appropriate attitude, can still carry grief in letting people go.

"If it's something that upsets you, let yourself feel upset about it," she says. "Accept people the way they are, but it doesn't necessarily mean that they're people that are healthy for you."

Sarkis describes the "let them" theory as a practice in detachment and a reminder that other people's choices are very rarely about us.

"Part of it is you're not villainizing the other person," she says. "You're realizing that their behavior is about them and not you."

You can 'let them' and still have boundaries

There are, of course, some situations where just saying "let them" doesn't suffice.

Del Toro says if someone is abusing or disrespecting you, then it's important to also take steps to seek appropriate help and safely remove yourself from the situation, rather than simply saying "let them."

It's also important to communicate proper boundaries to people, even if you decide to no longer take their actions personally. You also should intervene if someone you love is about to do something dangerous, she says, like drive under the influence.

"We need to also have boundaries," Del Toro says. "When it gets to a point where they are, again, disrespecting us or abusing us, then we don't 'let them.' "

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You should also makes sure you have communicated your needs to others before saying "let them" when they fall short. For instance, you and your partner should communicate your intentions for a relationship, before you say "let them" when they act contrary to the way you expect.

Overall, Del Toro says the "let them" theory can deliver profound insight into your relationships and where you may be exerting unnecessary control without even realizing it.

"It can be extremely helpful, so we want to try to implement this as much as possible," she says. "It'll also give you good insight as to how many situations in the past, or maybe even currently, still we do try to control.

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