Alive

I read on Wiki that the song was co-written with Adele about her life from her perspective.

When I read the lyrics it seems obvious that it has something to do with the pain she suffered at the hands of some kind of abuse. Whether it's mental, physical and or sexual is not clear. I don't think it matters.

The point of the song, is quite clear...despite all of the pain and abuse, she's alive and breathing. I take that to mean more than mere survival, but something along the lines of her vindication as a human being.

"You took it all, but I'm still breathing..." meaning, you took everything you possibly could from me, mentally, physically, emotionally, sexually...and despite that I have overcome your abuse. I'm Alive!

"I found solace in the strangest place Way in the back of my mind I saw my life in a stranger's face And it was mine"

I think this is about an internal struggle. I think this is written from the perspective of someone (apparently written for Adele) who has allowed themselves to steal their own joy, and they are aware that their own self "...took it all" through crippling anxiety and self doubt. In the song she finds peace in herself by discovering she allowed herself to become something she isn't. It is beautiful because the person climbs out of the darkness by admitting and taking ownership of their own demons and not placing blame on outside sources... powerful stuff.

As noted by other commenters, the song is written for Adele's perspective but I will refer to the protagonist as Sia anyway.

This first verse suggests that Sia did not have a positive or happy childhood. The "thunderstorm" could be representative of being born into an abusive household, and as such, she was forced to grow up quicker than a child should ("I grew up overnight") and had nobody there for her.

The second verse describes her immense longing for the lives that other people had that she thought were better than hers, especially love, which all children and people in general should be exposed to, but unfortunately Sia did not feel true love from anyone growing up. Despite this, she was ashamed of being envious towards these other people.

The pre-chorus describes Sia being in a hopeless situation. "One-way ticket to a place where all the demons go" refers to Sia feeling like she was in hell and couldn't get out. The wind not changing could refer to her situation never improving and feeling as if her world was permanently static.

The third verse explores Sia battling internal demons. The implications are that, growing up, Sia couldn't trust her own head and mind to the point where she couldn't even recognise herself, but now she is beginning to.

The bridge references an individual or multiple individuals that have torn Sia down in life ("you took it all", "you never noticed that I was in pain"). Despite being torn down to such brutal extent, Sia remained resilient and found confidence, ultimately proving everyone who doubted her wrong.

Additionally, I forget the details exactly, but Sia detailed the phrase "I'm still breathing" coming from a reality show she watches in which someone was asked if they were okay, to which they simply responded "I'm still breathing". Despite the motivation and strength of the song's protagonist, they still may not necessarily be okay but are still doing their best.