I have a diagnosed MH condition that I actively and almost religiously get help for and have done for years. I don't want it. I don't want to burden anybody or imply that it's the responsibility of friends and family to fix anything. It isn't organic, it's basically massive psychological injury I have to live with.
I believed the claptrap about telling people around me. I told my closest friends. I then discovered that as I hadn't healed in a timely manner, some didn't want to be around me. I cannot explain how isolating that is. Living with the impact of this mental injury is a daily punishment for other people's actions, so to be punished for not being "back to normal" in their eyes quickly enough felt like a second punishment. And of course, what "back to normal" meant was how I was before they knew I was struggling, aka when I was pretending.
However, a friend of a friend has been battling a rare form of cancer for years and while it's a miracle he's still alive, he's lost a lot of friends too. A great many people actually don't want to remain in contact with someone who is long term struggling, because it ties them down to a greater or lesser extent, from enjoying their own life. Not everyone, but these people definitely exist.
On the other side, a close friend of mine was an alcoholic who was drinking and was destroying her life. I stood by her, listened to her ranting and raving, I pushed her to get on a therapy waiting list, offered to come with her once therapy started, stood by her when she was struggling not to drink and when the medications made her feel bad. The cycles of this were awful. I was honest with her though - I didn't passively listen when she was sober. But when it got to the point she moved a guy off the internet she'd not met into her house (she was drunk) I couldn't cope. I couldn't do anything to stop it and it was during homeschooling period of covid and I was losing my mind with that anyway. I cared so much that I couldn't bear seeing her do this. I told her it wasn't sensible and I stopped answering her calls for about a month until I'd got myself sorted again, then I got back in touch. We're good friends again and she's not been drinking for a couple of years. I still feel guilty for dropping her like that but it was so horrific and she was drunk on every call, forgetting what she'd said the day before, that I didn't see a point in trying to explain it anyway.