Selena Gomez and Demi Lovato were both Barney actresses before becoming Disney stars as teens. Since then, though, their lives have taken down different paths -- each with their own claims to fame, their own successes, and their own struggles.

Demi recently shared a lot about herself in a documentary, showing how far she's come but revealing that she still has a ways to go.

And who spoke up to praise her for her honesty and bravery but Selena Gomez.

Selena Gomez revealed her Lupus diagnosis back in 2015.

The illness, which was constantly mentioned on House back in that medical drama's heyday, involves Selena's own autoimmune system attacking her healthy organs, perceiving them as intruders.

Despite modern medicine, Lupus can still be deadly.

Even with drastic treatments, including chemotherapy, Lupus has taken its toll on Selena Gomez, forcing her to undergo a kidney transplant in secret earlier this year. 

It was actually her friend, Francia Raisa, who donated her kidney to Selena in a life-saving display of friendship and generosity. 

Selena's ongoing battle with Lupus has forced her to take multiple extended breaks from her career as an actress and from being one of the greatest singers on the face of the Earth.

Honestly, as wonderful as it is that she was able to receive a kidney transplant, that's not a cure. It's a short-term solution for one particular problem.

Some people are genuinely afraid that Lupus will claim Selena's life.

Demi Lovato has had more than her share of struggles too, however.

In fact, Demi recently shared before and after eating disorder photos, highlighting her dramatic transition into being and feeling so much healthier.

She's also spoken at length about mental health -- about bipolar disorder and especially about the debilitating effects of depression.

Contrary to what some people might suggest, just because Demi's illnesses are psychological doesn't make them her fault.

And it doesn't make them somehow more deserved than Selena's Lupus or anyone's anything.

Demi shared bits of her life and struggles in her documentary, Simply Complicated. But Demi also talks about how much personal progress she's made.

Demi promoted her documentary, which is on YouTube, via Instagram.

Selena Gomez left an Instagram comment for all to see.

"This was beautiful. I’m so happy for you."

Recently, Demi's life has been full of many good things for her to celebrate.

Selena's praise continues:

"You always continue to [be] bold and real. I wish more people were like you. Love you."

That is so wholesome.

The world really would be a better place if more people were like Demi Lovato. Or like Selena.

In the documentary, Demi speaks directly about her continuing battle with her eating disorder.

"When I feel lonely, my heart feels hungry and then I end up binging and I don’t know how to figure out how to be alone."

A lot of people eat emotionally, even when they aren't hungry. Demi's situation is a bit more severe, which is why this is called a disorder.

(Which means that solutions that work for most of us, like "oh I'll knit instead of eating" or "just play video games that keep your hands busy" aren't as helpful for people who might compulsively overeat)

"One thing that I haven’t fully conquered is my eating disorder."

Eating disorders usually work a little like alcoholism -- you might recover, but you never have a "normal" relationship with food.

"Food is still the biggest challenge in my life. It’s something that I’m constantly thinking about."

That part is almost universally relatable, right? I've been thinking about what I'm going to eat today since last night.

What makes it a disorder is that Demi has, in the past, struggled to stop herself from overeating -- and then she dealt with self-loathing issues by throwing up.

That's bulimia, folks.

Understanding that those battling mental illness aren't just grappling with neurotypical impulses is important.

It's good that Selena Gomez has so much empathy for her friend.

And it's good that both of these talented stars are sharing their stories.